To improve the fabricating quality of overhanging structure in selective laser melting (SLM), the computer-aided optimization of process parameters is studied, which focuses on the fabrication orientation and the power input. The optimization model of the fabrication orientation, which is aiming at reducing the difficultly fabricating overhanging surface area, is proposed. The genetic solution for the model is studied. The static lookup table to adjust the energy input duly is built by traversing all the triangles in the stereo lithography (STL) file. The experimental results show that the difficultly fabricating overhanging surface area reduces from 555.12 mm2 to 16.211 mm2 after the optimization of the fabrication orientation, which leads to the less support needs, and the fabrication quality is obviously improved without so much overhang and deformation.