The work aims to improve the surface quality of the 316L stainless steel formed by the selective laser melting (SLM), so as to achieve the high-quality and high-efficiency forming effects. SLM forming was performed with a laser power of 380 W. The formation mechanism of defects on surface and cross section of 316L stainless steel was tested and studied based on high layer thickness of 160 μm and high scanning speed over 1000 mm/s to determine the surface morphology, density, micro-structure, mechanical properties, etc. and explore the process of high-quality and high-efficiency printing and forming of 316L. The surface defects of SLM forming 316L stainless steel were mainly spheroidization, lap, and poor fusion between molten pools. The cross-section defects mainly consisted of pores, spheroidization, and poor fusion between molten pools. The exposure time had the greatest influence on the quality of the high layer thickness forming section, and increasing the exposure time improved the forming density; while the smaller exposure time, point distance and hatch space were more favorable for high scanning speed forming. Under the high scanning speed experimental conditions of 1000 mm/s, namely that the exposure time, point distance and hatch space were 30 μs, 30 μm, and 90 μm, respectively, the density of the test piece reached 99.99%. The quality of cross section formed by high rate can achieve high density through process optimization combination, and the surface re-melting process improves the surface effect obviously. Therefore, the overall performance is optimal. High layer thickness parameter printing can achieve high density, but has large difference from the high rate forming parameters in surface quality. After comprehensive comparison, high rate forming can achieve the high density under the premise of ensuring better surface quality.