The SLS (Selective Laser Sintering, SLS) technology can directly manufacturing any complex structure, however, due to the limitation of the manufacturing engineering factor, the surface quality and the dimension accuracy of the green part are still an outstanding problem. So, the experimental methods were adopted to study the effect of part orientation on the machining accuracy, the part orientation will significantly affects the outline of the part due to the stair-stepping phenomenon, and then affects the surface quality and the dimension accuracy. The experimental samples of different part orientations including 0, 20, 45, 60, 90 degree were fabricated, and the results indicated that the stair-stepping phenomenon significantly affected by the part orientation, when the part orientation is 0, 45 and 90 degree, the dimension accuracy is best than other part orientation, it mean the stair-stepping phenomenon is smallest. So, when the part structure is complicated, the important structure dimension should be chosen the orientation 0, 45, or 90 degree.