Abstract: Selective laser melting (SLM) is one of the most widely used metal additive manufacturing techniques. Many defects are inevitably produced in the SLM formed parts, including pores, surface layer powder spheroidization, cracks and so on. The formation of defects not only affect the smoothness of the forming process, but also damage the internal integrity of the part and reduce its serviceability. The main characteristics of three defects including pores, surface layer powder spheroidization and cracks in SLM formed 316L stainless steel parts are reviewed. The formation mechanisms and influencing factors of these three defects are summarised, and the main measures to control the defects are proposed. Finally, future research directions are put forword.