In order to make up the deficiency of discrete state recognition in motion process prediction, a motion intent recognition method for human joint angle prediction is proposed. The driver circuit and echo acquisition program were designed for the A-mode ultrasound probe to measure the muscle thickness. The motion data of 6 volunteers were collected. A customized mapping relation model was generated after fitting the data of muscle thickness and joint angle during the same movement. The average value of the coefficient of determination R 2 is 0. 916 9, which shows a good matching degree. The system’s output response frequency of predictive value can reach 30 Hz when the model was solidified into the program, which indicates that the method can track the continuous state changes in the process and recognize the human motion intent. Compared with the discrete state recognition method, it can effectively improve the recognition precision and real-time performance.