Abstract: The mechanical properties of skeletal muscles are always related to their architectural changes.Ultrasound is a useful tool to study skeletal muscle that can be used to monitor dimensional architectural changes of muscle.In this paper,ultrasound measurement of motion and elasticity system is introduced,which can synchronously and continuously acquire different kinds of data including ultrasound signals,EMG signals,angle,force,etc.,without disturbance.Based on this system,the locomotory track of muscle thickness of extensor carpi radialis is obtained with a correlation tracking algorithm during wrist flexion-extension.The results show that the correlation-tracking algorithm is simple,fast,and accurate.They also prove that relation between wrist angle and muscle thickness of extensor carpi radialis is nonlinear.The study of skeletal muscle with multi-parameters is feasible.