According to the study on seat-back curves about different people, the method that using two arc-shaped roofs to give back supporting force of the human body is proposed. Through a clever design application of piezoelectric sensor, microcontroller, motors, and arc-shaped roofs form a closed loop control system. Through the design of horizontal and vertical adjustment mechanism, a flexible and adaptive multi-dimensional back can reduce the harm to human spine which caused by poor posture and sedentary life style. Model building and stress analysis are done by Inventor software to verify the mechanism of strength. According to the study on seat-back curves about different people, the method that uses two arc-shaped roofs to give back supporting force of the human body is proposed. Through a clever design application of piezoelectric sensor, microcontroller, motors, and arc- shaped roofs form a closed loop control system. Through the design of horizontal and vertical adjustment mechanism, a flexible and adaptive multi-dimensional back can reduce the harm to human spine which caused by poor posture and sedentary life style. Model building and stress analysis are done by Inventor software to verify the mechanism of strength.