Aimed at the effect of load changed on Stewart platform of flight simulator, the dynamics model of flight simulator Stewart platform and its load was established by using the mechanical dynamics software ADAMS. The joint simulation platform for simulation analysis with MATLAB software was established, and the sport trajectory of flight simulator was obtained with load or no load and load changed. The effect of PID control parameters was analyzed. Eventually the range of deviation from the set position for centroid is obtained, and its simulation data provide a theoretical basis for the actual control and mechanical design.