diff --git a/samples/helloworld.ks b/samples/helloworld.ks
index 3a5d9f4..563ecc5 100644
--- a/samples/helloworld.ks
+++ b/samples/helloworld.ks
@@ -1,5 +1,6 @@
 
 mod D:\code\rs\key-native\target\debug\key_native.dll> m
 
-let 😂😂 = 20
-log(😂😂)
+let o = [2,"s",99]
+o[1] = 111
+log(o)
diff --git a/spec/ops.md b/spec/ops.md
index a3fe93c..1f7fb4c 100644
--- a/spec/ops.md
+++ b/spec/ops.md
@@ -46,4 +46,14 @@ Str, Instance, List, Obj也依照以上算法比较。
 使用连等：
 为了减少无意义的数据复制，目前赋值语句只返回uninit，所以连等并不可用。
 
-一元运算符优先级比二元运算符高
\ No newline at end of file
+一元运算符优先级比二元运算符高
+
+index[]
+以下类型可以使用索引
+Buffer 返回Uint,在下标无效时返回uninit
+List 返回对应槽位的值
+Inst 类实例传入下标可以无视可见性读取第n个属性
+Str 获取第i个unicode字符(性能较差,请用迭代器替代)
+Uint 传入小于64的数字,返回Bool,代表从右到左的二进制第i位是否为1
+
+index不会报错,在遇到问题时会直接返回uninit
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index 18b7dc2..ae1147b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -25,6 +25,7 @@ fn main()-> ExitCode {
   // }));
 
   // index
+  // 迭代器 loop
   // 基本类型的方法，也就是所有litr的prop
 
   // 析构函数..?
diff --git a/src/runtime/calc.rs b/src/runtime/calc.rs
index 528b466..0774514 100644
--- a/src/runtime/calc.rs
+++ b/src/runtime/calc.rs
@@ -17,6 +17,9 @@ impl CalcRef {
       CalcRef::Own(v)=> v
     }
   }
+  pub fn uninit()-> Self {
+    CalcRef::Own(Litr::Uninit)
+  }
 }
 impl std::ops::Deref for CalcRef {
   type Target = Litr;
@@ -41,10 +44,11 @@ impl Scope {
   /// 
   /// 该函数必定发生复制
   pub fn calc(&mut self,e:&Expr)-> Litr {
-    use Litr::*;
     match e {
       Expr::Call { args, targ }=> self.call(args, targ),
 
+      Expr::Index { left, i }=> calc_index(self, left, i).own(),
+
       Expr::Literal(litr)=> litr.clone(),
 
       Expr::Variant(id)=> self.var(*id).clone(),
@@ -60,6 +64,7 @@ impl Scope {
 
       // 一元运算符
       Expr::Unary{right, op}=> {
+        use Litr::*;
         let right = self.calc_ref(right);
         match op {
           b'-'=> {
@@ -237,6 +242,7 @@ impl Scope {
         let mut from = self.calc_ref(&e);
         get_prop(self, &mut *from, *find)
       }
+      Expr::Index { left, i }=> calc_index(self, left, i),
       Expr::Variant(id)=> CalcRef::Ref(self.var(*id)),
       // todo: Expr::Index
       _=> {
@@ -275,7 +281,10 @@ fn expr_set(this:&mut Scope, left:&Expr, right:Litr) {
         let (rf, scope) = this.var_with_scope(*id);
         (CalcRef::Ref(rf), scope)
       }
-      // todo: Expr::Index
+      Expr::Index{left, i}=> {
+        let (mut from, scope) = calc_ref_with_scope(this, &left);
+        (calc_index(this, left, i), scope)
+      }
       _=> {
         let v = this.calc(e);
         // 如果是需要计算的量，就代表其作用域就在this
@@ -301,7 +310,20 @@ fn expr_set(this:&mut Scope, left:&Expr, right:Litr) {
         _=> *get_prop(this, &mut left, *find) = right
       }
     }
-    // todo Expr::Index
+    Expr::Index{left,i}=> {
+      let (mut left, scope) = calc_ref_with_scope(this, &left);
+      let i = match this.calc(i) {
+        Litr::Int(n)=> n as usize,
+        Litr::Uint(n)=> n,
+        _=> err!("Index必须是整数")
+      };
+      may_add_ref(&right, scope);
+      if let Litr::Ninst(inst) = &mut *left {
+        (unsafe{&*inst.cls}.isetter)(inst, i, right)
+      }else {
+        *index(left, i) = right;
+      }
+    }
     _=>{
       let (mut left, scope) = calc_ref_with_scope(this, left);
       may_add_ref(&right, scope);
@@ -373,6 +395,45 @@ fn get_prop(this:&Scope, from:&mut Litr, find:Interned)-> CalcRef {
   }
 }
 
+fn calc_index(this:&mut Scope, left:&Box<Expr>, i:&Box<Expr>)-> CalcRef {
+  let mut left = this.calc_ref(left);
+  let i = match this.calc(i) {
+    Litr::Int(n)=> n as usize,
+    Litr::Uint(n)=> n,
+    _=> err!("Index必须是整数")
+  };
+  index(left, i)
+}
+fn index(mut left:CalcRef, i:usize)-> CalcRef {
+  match &mut *left {
+    Litr::Buffer(v)=> {
+      if i>=v.len() {return CalcRef::uninit()}
+      CalcRef::Own(Litr::Uint(v[i] as usize))
+    }
+    Litr::List(v)=> {
+      if i>=v.len() {return CalcRef::uninit()}
+      CalcRef::Ref(&mut v[i])
+    }
+    Litr::Inst(v)=> {
+      if i>=v.v.len() {return CalcRef::uninit()}
+      CalcRef::Ref(&mut v.v[i])
+    }
+    Litr::Ninst(v)=> {
+      CalcRef::Own((unsafe{&*v.cls}.igetter)(v, i))
+    }
+    Litr::Str(n)=> {
+      match n.chars().nth(i) {
+        Some(c)=> CalcRef::Own(Litr::Str(c.to_string())),
+        None=> CalcRef::uninit()
+      }
+    }
+    Litr::Uint(n)=> {
+      if i>=64 {return CalcRef::Own(Litr::Bool(false));}
+      CalcRef::Own(Litr::Bool((*n & (1<<i)) != 0))
+    }
+    _=> CalcRef::uninit()
+  }
+}
 
 fn binary(this:&mut Scope, left:&Box<Expr>, right:&Box<Expr>, op:&Box<[u8]>)-> Litr {
   use Litr::*;
diff --git a/src/runtime/outlive.rs b/src/runtime/outlive.rs
index 516c29b..0f1205d 100644
--- a/src/runtime/outlive.rs
+++ b/src/runtime/outlive.rs
@@ -116,6 +116,6 @@ pub fn may_add_ref(v:&crate::scan::literal::Litr, target_scope: Scope) {
     Litr::Inst(inst)=> 
       inst.v.iter().for_each(|item|may_add_ref(item, target_scope)),
     Litr::Obj(map)=> map.values().for_each(|item|may_add_ref(item, target_scope)),
-    _=> {}
+    _=> ()
   }
 }
diff --git a/src/scan/expr.rs b/src/scan/expr.rs
index 63cb524..e2da92f 100644
--- a/src/scan/expr.rs
+++ b/src/scan/expr.rs
@@ -31,6 +31,10 @@ pub enum Expr {
     args: Vec<Expr>,
     targ: Box<Expr>
   },
+  Index{
+    left: Box<Expr>,
+    i: Box<Expr>
+  },
   // 创建实例
   NewInst{
     cls: Interned,
@@ -139,9 +143,9 @@ impl Scanner<'_> {
   
       // 如果此运算符是括号就代表call
       if op == b"(" {
-        let targ = Box::new(expr_stack.pop().unwrap());
         self.next();
         self.spaces();
+        let targ = Box::new(expr_stack.pop().unwrap());
         let mut args = Vec::new();
         loop {
           let e = self.expr();
@@ -163,7 +167,23 @@ impl Scanner<'_> {
           args, targ
         });
         continue;
-      };
+      }
+
+      // 如果此运算符是方括号就代表index
+      if op == b"[" {
+        self.next();
+        self.spaces();
+        let left = Box::new(expr_stack.pop().unwrap());
+        let i = Box::new(self.expr());
+        if self.i() >= self.src.len() || self.cur() != b']' {
+          self.err("未闭合的右括号']'。");
+        }
+        self.next();
+        expr_stack.push(Expr::Index{
+          left, i
+        });
+        continue;
+      }
   
       // 将新运算符和它右边的值推进栈
       self.spaces();