In order to reduce electromagnetic noise of the electric vehicle and calculate electromagnetic radial force, a finite element parametric model is built up based on permanent magnet synchronous motor in the electric vehicle. By means of analytical method and experimental method, the model proves to be right. Based on the model, sensitivity analysis for structural determinants that can effect electromagnetic radial force is carried out, which takes the thickness of permanent magnet, the length of air gap, the width of stator slot center and the width of stator slot shedding as variables and minimum first order, second order, third order radial force energy and mean value of radial force as target function. Combined with the design requirements of motor, optimization scheme is proposed, in which the length of air gap and the width of stator slot center are as parameter optimization. According to the finite element computing result, the optimization scheme improves the radial force.