diff --git a/src/problem/mod.rs b/src/problem/mod.rs
index 4272816..bbc0641 100644
--- a/src/problem/mod.rs
+++ b/src/problem/mod.rs
@@ -190,4 +190,5 @@ mod p136_single_number;
 mod p137_single_number_ii;
 mod p201_bitwise_and_of_numbers_range;
 mod p66_plus_one;
-mod p172_factorial_trailing_zeroes;
\ No newline at end of file
+mod p172_factorial_trailing_zeroes;
+mod p69_sqrtx;
\ No newline at end of file
diff --git a/src/problem/p69_sqrtx.rs b/src/problem/p69_sqrtx.rs
new file mode 100644
index 0000000..09b6630
--- /dev/null
+++ b/src/problem/p69_sqrtx.rs
@@ -0,0 +1,46 @@
+
+/**
+ * [69] Sqrt(x)
+ */
+pub struct Solution {}
+
+
+// submission codes start here
+
+impl Solution {
+    pub fn my_sqrt(x: i32) -> i32 {
+        // 牛顿迭代法
+        if x == 0 {
+            return 0;
+        }
+        
+        let c = x as f64;
+        let mut x = x as f64;
+
+        loop {
+            let xi = 0.5 * (x + c / x);
+            if (x - xi).abs() < 1e-7 {
+                break;
+            }
+            x = xi;
+        }
+        
+        return x as i32;
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_69() {
+        assert_eq!(0, Solution::my_sqrt(0));
+        assert_eq!(1, Solution::my_sqrt(1));
+        assert_eq!(1, Solution::my_sqrt(2));
+        assert_eq!(2, Solution::my_sqrt(4));
+        assert_eq!(2, Solution::my_sqrt(8));
+    }
+}