Objective The knee-ankle-toe active prosthesis system has strong coupling characteristics in the stance phase. Due to its strong coupling, the control precision of prosthesis system is low. To solve this problem, the method of exact feedback linearization is proposed and used to decouple the active transfemoral prosthesis system. Methods Firstly, the gait information of human lower limbs is collected. The stance phase is divided into the early and middle stance phase and the last stance phase. The dynamic model of stance phase is established. Secondly, in the stance phase, the prosthesis system is decoupled based on the exact feedback linearization decoupling. The integral sliding mode controller is designed to control the active transfemoral prosthesis. Finally, a co-simulation platform is built to verify the effectiveness of the method. Results The decoupled system can improve the control accuracy. After decoupling, the calculated mean absolute error ( MAE ) of knee and ankle in the early and middle stance phase is reduced to 0.0011 degrees and 0.0026 degrees respectively. Root mean square error ( RMSE ) is reduced to 0.0147 degrees and 0.0236 degrees respectively. At the last stance phase, the MAE of knee, ankle and toe is reduced to 0.0111,0.0051 and 0.0065 degrees respectively, and the RMSE is reduced to 0.0219,0.0210 and 0.0129 degrees respectively. The overall control error is reduced and the response speed is accelerated. And the prosthesis can operate stably in the co-simulation environment. Conclusions The decoupling method proposed in this paper can effectively realize the decoupling of the transfemoral prosthesis system and provide the basis for the prosthetic system.