diff --git a/to_int64.go b/to_int64.go
index 51633a9..5825db8 100644
--- a/to_int64.go
+++ b/to_int64.go
@@ -2,7 +2,7 @@ package convx
 
 import (
 	"errors"
-	"strconv"
+	"math/big"
 )
 
 // interface 转 int64
@@ -37,7 +37,15 @@ func ToInt64(val interface{}) (i int64, err error) {
 	case float64:
 		return int64(v), nil
 	case string:
-		return strconv.ParseInt(v, 10, 64)
+		num := new(big.Float)
+		_, ok := num.SetString(v)
+		if !ok {
+			return 0, errors.New("convx.ToInt64: out of range")
+		}
+
+		i, _ := num.Int64()
+		// fmt.Println(val, i, b)
+		return i, nil
 	case bool:
 		if v {
 			return 1, nil
@@ -47,4 +55,3 @@ func ToInt64(val interface{}) (i int64, err error) {
 	}
 	return 0, errors.New("convx.ToInt64: unknown type")
 }
-
diff --git a/to_int64_test.go b/to_int64_test.go
index cfd2fd2..f4e841a 100644
--- a/to_int64_test.go
+++ b/to_int64_test.go
@@ -12,30 +12,34 @@ func TestToInt64(t *testing.T) {
 		output  int64
 		isError bool
 	}{
-		{"123", 123, false},
-		{123.456, 123, false},
-		{true, 1, false},
-		{"abc", 0, true}, //
-		{nil, 0, true},
-		{123, 123, false},
-		{int32(123), 123, false},
-		{uint64(123), 123, false},
-		{int64(123), 123, false},
-		{float32(123.456), 123, false},
-		{float64(123.456), 123, false},
-		{"-123", -123, false},
-		{"123.456", 123, false}, // TODO: should be 123
+		{"123", 123, false},            // string
+		{123.456, 123, false},          // float64
+		{true, 1, false},               // bool
+		{"abc", 0, true},               // string
+		{nil, 0, true},                 // nil
+		{123, 123, false},              // int
+		{int32(123), 123, false},       // int32
+		{uint64(123), 123, false},      // uint64
+		{int64(123), 123, false},       // int64
+		{float32(123.456), 123, false}, // float32
+		{float64(123.456), 123, false}, // float64
+		{"-123", -123, false},          // string
+		{"123.456", 123, false},        // string
 		{"170141183460469231731687303715884105727", 9223372036854775807, false},   // max int64
 		{"-170141183460469231731687303715884105728", -9223372036854775808, false}, // min int64
 		{"9223372036854775807", 9223372036854775807, false},                       // max int64
 		{"-9223372036854775808", -9223372036854775808, false},                     // min int64
-		{"12345678901234567890", 0, false},                                        // too large
+		{"12345678901234567890", 9223372036854775807, false},                      // too large
 
 	}
-	for _, test := range tests {
+	for idx, test := range tests {
 		output, err := convx.ToInt64(test.input)
-		if err != nil {
-			t.Error("ToInt64(", test.input, ") should not return error")
+		if test.isError && err == nil {
+			t.Error(idx, ": ToInt64(", test.input, ") should return error")
+			continue
+		} else if !test.isError && err != nil {
+			t.Error(idx, ": ToInt64(", test.input, ") should not return error", err.Error())
+			continue
 		}
 		if output != test.output {
 			t.Error("ToInt64(", test.input, ") should be", test.output, "but was", output)