This paper presents control method for human assist using chain mechanism system. Human assist systems are critical item for us. In Japan, we need support of robot in the medical and welfare fields. This study notices the wearable assist robot using chain mechanism. Chain mechanism has some good point. For example, it doesn't have to wear for the legs directly. However this system has the interference between motors and Joints. To solve this problem, we propose a method using the transformation matrix. It is guided by the structure of this system. We tested to confirm if this matrix is true or not. The method of confirmation is to control joint position. As a result of this, we can prove the transformation matrix is accurate and model the system.