Considering the influence of processing parameters and model shape parameters of selective laser melting on the forming quality of the part, four levels of five factors, such as contour laser power, filling laser power, scanning speed, scanning distance and shape parameters, were selected to carry out the orthogonal experiment. The influence of these five parameters on the surface roughness, X/Y dimensional accuracy and the profile error of circular surface is studied. In order to evaluate the forming accuracy synthetically, the multi-objective optimization model is established. In order to facilitate calculation, the weighted method is used to turn the multi-objective into single objective optimization. The final results show that the precision of the printed parts is the best when the filling laser power is 210 kW, the scanning distance is 0.09 mm, the surface laser power is 160 kW and the scanning speed is 1 100 mm s-1. At the same time, the results also show that the shape parameters of the parts have some influence on the precision of the parts.