diff --git a/src/Contracts/Types/Str.php b/src/Contracts/Types/Str.php
new file mode 100644
index 0000000..9ffc06d
--- /dev/null
+++ b/src/Contracts/Types/Str.php
@@ -0,0 +1,49 @@
+<?php
+
+/**
+ * This file is part of web3.php package.
+ * 
+ * (c) Kuan-Cheng,Lai <alk03073135@gmail.com>
+ * 
+ * @author Peter Lai <alk03073135@gmail.com>
+ * @license MIT
+ */
+
+namespace Web3\Contracts\Types;
+
+use Web3\Contracts\SolidityType;
+use Web3\Contracts\Types\IType;
+
+class Str extends SolidityType implements IType
+{
+    /**
+     * construct
+     * 
+     * @return void
+     */
+    public function __construct()
+    {
+        //
+    }
+
+    /**
+     * isType
+     * 
+     * @param string $name
+     * @return bool
+     */
+    public function isType($name)
+    {
+        return (preg_match('/string(\[([0-9]+)\])*/', $name) === 1);
+    }
+
+    /**
+     * isDynamicType
+     * 
+     * @return bool
+     */
+    public function isDynamicType()
+    {
+        return true;
+    }
+}
\ No newline at end of file
diff --git a/test/unit/StrTypeTest.php b/test/unit/StrTypeTest.php
new file mode 100644
index 0000000..74f3309
--- /dev/null
+++ b/test/unit/StrTypeTest.php
@@ -0,0 +1,69 @@
+<?php
+
+namespace Test\Unit;
+
+use InvalidArgumentException;
+use Test\TestCase;
+use Web3\Contracts\Types\Str;
+
+class StrTypeTest extends TestCase
+{
+    /**
+     * testTypes
+     * 
+     * @var array
+     */
+    protected $testTypes = [
+        [
+            'value' => 'string',
+            'result' => true
+        ], [
+            'value' => 'string[]',
+            'result' => true
+        ], [
+            'value' => 'string[4]',
+            'result' => true
+        ], [
+            'value' => 'string[][]',
+            'result' => true
+        ], [
+            'value' => 'string[3][]',
+            'result' => true
+        ], [
+            'value' => 'string[][6][]',
+            'result' => true
+        ],
+    ];
+
+    /**
+     * solidityType
+     * 
+     * @var \Web3\Contracts\SolidityType
+     */
+    protected $solidityType;
+
+    /**
+     * setUp
+     * 
+     * @return void
+     */
+    public function setUp()
+    {
+        parent::setUp();
+        $this->solidityType = new Str;
+    }
+
+    /**
+     * testIsType
+     * 
+     * @return void
+     */
+    public function testIsType()
+    {
+        $solidityType = $this->solidityType;
+
+        foreach ($this->testTypes as $type) {
+            $this->assertEquals($solidityType->isType($type['value']), $type['result']);
+        }
+    }
+}
\ No newline at end of file