This study aims to investigate the effect of microstructure on mechanical properties of the GH3536 alloy fabricated by selective laser melting (SLM) technology. Different powder batches are utilized to fabricate the specimens. The microstructures, room temperature tensile property, and high temperature endurance performance are then tested, and the invalidation mechanism is analyzed. The results show that the microstructure of the SLM GH3536 alloy is mainly austenitic phase with M23C6 inside the grain and at the grain boundary. The amount of grain boundary decreases with the increasing grain size, leading to an improvement of the high temperature endurance performance, but a degradation of the tensile property at room temperature. The massive carbide at the grain boundary will reduce the room temperature tensile property and the high temperature endurance performance of the SLM GH3536 alloy. However, the chain carbide at the boundary can improve the room temperature tensile property and high temperature endurance performance.