This study aims to develop a controller and graphical user interface for validating the gait performance of a prototype knee prosthesis. Current research on knee prostheses focuses on developing hybrid systems that combine passive and active walking modules. Therefore, it is essential to conduct gait function validation experiments for modules, and clinical gait trials. Previous studies have validated the gait function of assistive devices through simulations or conducted clinical trials where patients wore backpacks containing the controller, instrumentation, and batteries. However, validating gait performance in virtual reality has limitations, and studies have shown that wearing a backpack during walking can affect gait. This study aims to address and improve upon these limitations. The controller developed in this study includes five essential experimental functions. First, it measures the response time of the passive walking module to validate its performance in adapting to changes in gait events. Second, it evaluates the initial assembly condition of the active walking module. Third, it measures the maximum degrees per second of the active walking module, assessing speed at different knee angles during the swing phase. Fourth, it measures the maximum torque of the active walking module to pre-assess its ability to provide the necessary torque for transfemoral amputees when descending stairs or slopes. Finally, the gait algorithm is validated in a real walking environment. These five experiments validate the mechanical gait performance and the software-based gait algorithm of the knee prosthesis, promoting the development of high-quality knee prostheses and improving the quality of life for knee amputees.