The performance simulation for a spark ignition Wankel Rotary Engine is presented in this paper. Geometric models of housing and rotor are employed for evaluating volume of chamber at each eccentric shaft angle. A thermodynamic model is employed, which includes the first law of thermodynamics, combustion and convective heat transfer from chamber contents to surroundings. A thermochemical equilibrium model, which considers 10 species - CO, CO2, O2, H2, H2O, OH, H, O, NO, and N2 in the burned gas region, is also employed. 4 processes of gas exchange, compression, combustion and expansion process are considered, while the pressure, the temperature and the compositions of chamber gas at each eccentric shaft angle in each process are computed in this performance simulation.Meanwhile, Interactive Computer Graphic Animation is made to assist the accomplishment of parametric study with various geometry data.This performance simulation could be useful for optimal design of spark ignition Wankel Rotary Engine with parametric study for various design parameters or operating conditions.