Abstract: A numerical modelling is proposed to calculate the pumping performance of sputter ion pump(SIP).The discharge parameters in Penning cell,sputtering ion energy and angle are obtained by COMOL Multiphysics plasma mode coupled with electromagnetic field mode.The sputtering yield and pumping speed of a Penning cell are calculated based on the sputtering yield semi empirical formalism.The numerical calculation results agree well with the experimental data,which shows that the present numerical modelling is validated.The effects of gap between anode and cathode of SIP Penning cell on the pumping performance is studied by the numerical method.The simulation results shown that the gap between anode cell and cathode plate is an important factor effected on the effective pumping speed.The effective pumping speeds increase first and then decrease as the gap increases.There is a gap between anode and cathode make pumping speed get peak value,which will be large as the radius of anode cell increases.A new SIP structure composed of different height and radius Penning cells is improved to optimize the pumping performance.