To research the sitting posture comfort evaluation method, through the example of comfort evaluation of the ergonomic seat and standard office seat, a methodology is introduced to evaluate the sitting posture comfort combining ergonomics theory. The proposed method is based on optical motion capture system, pressure sensor and JACK software, and TRC file is acquired by using EVART real-time capture software for identifying the spatial motion trail of human body. Then MATLAB software is used to analyze the human body motion data, and the sitting posture angle difference data for human body in different seats is acquired. TRC file is loaded into JACK software, and with the TAT REPORTER of JACK software, muscle force, moment of force and fatigue data, etc. are output, which are compared with the actual measured data from experiments, and ergonomics method is used for the evaluation. The result shows that the method of considering joint angles combining JACK software for data output is effective for evaluating sitting comfort.