The formation of H13 steel powder material is conducted by using the selective laser melting(SLM) technology, and the influence rules of process parameters on the forming defects are obtained via a comparative study by changing the parameters including laser power, scanning speed, scanning pitch and scanning method. The results show that, in a certain range, the increase of laser power or the decrease of scanning speed is beneficial to the formation of parts. A too large or too small scanning pitch has a significant impact on the forming quality and thus the pores or fusion-incomplete defects occur. The quality of forming parts under S-shaped orthogonal scanning is the best if compared with those under Z-shaped orthogonal scanning and single X-direction scanning.