The single-scan track and block experiment of 200 μm large layer-thickness gas atomized 316L powder by the selective laser melting (SLM) technique is conducted. Through the analysis of densities, microstructures, tensile properties and defect mechanism of forming parts, the process is optimized. The results show that the density is up to 99.99% when the exposure time is 120-160 μs, the overlap rate is 50%-60% and laser power is 400 W. The unmelted defects occurred during the SLM process can be removed by the adjustment of process parameters. Although the micropores and balling defects cannot be completely eradicated, a short exposure time can be used to reduce the balling size. The equiaxed crystals and columnar crystals can be observed in the microstructures of samples. The yield strength, tensile strength and elongation rate of these samples are 530 MPa, 635 MPa and 31%, respectively, indicating that there exists a nice tensile property.