Objective To simulate the instantaneous central trajectory of four-bar artificial knee joint and to analyze the stability of the prosthetic system. Methods By establishing a model for the instantaneous center trajectory and the stability of four-bar artificial limb knee, a simulation software package was developed based on LabView programming platform. Results The dynamic trajectory of the instantaneous center of four-bar artificial knee joint was simulated in the developed software system, showed in animation, and calculated the value of x/y – the value of the hip torque needed to maintain the body’s stability, and saved the relevant data. Compared to actual data, the software could accurately describe the instantaneous center of four-bar artificial knee joint. Conclusion Preliminary test results showed that the developed software system was able to provide both visual display and numerical results of the instantaneous central trajectory of four-bar artificial knee joint and its stability. These would help engineers and clinicians in the design and optimization of four-bar artificial knee joint mechanisms.