Abstract: A single point incremental forming of AZ31B magnesium alloy, under different conditions of forming temperature, interlayer spacing and feed rate, were studied by numerical simulation. And then the response surface models showing the effects of the process parameters on the maximum Mises stresses and the maximum thickness reduction rates were established. Furthermore, a multi-objective optimization design was carried out with the maximum Mises stress and maximum thickness reduction rate as constraints. The results show that the temperature rise of sheet metal reduced with the increase of forming temperature. Especially when the forming temperature was over 200℃, the temperatures at different spots of the sheet metal changed little. The significance of the effects of the parameters on the maximum Mises stress or on the maximum thickness reduction rate were ranked from big to small as follows:forming temperature, feed rate and interlayer spacing. The optimal process parameters obtained by the multi-objective optimization were listed as follows:forming temperature of 273℃, interlayer spacing of 0.51 mm and feed rate of 1 340 mm·min^-1. With the optimal process parameters, the errors between the simulated and measured thickness of the forming part were relatively small, indicating the accuracy of the numerical simulation model and the response surface model.