Abstract: The density, microstructure and mechanical properties of 4J36 invar alloy formed by selective laser melting with different laser power and scanning speed were analyzed by single factor test.The optimal forming process was determined.The thermal expansion coefficient of the formed and heat treated samples was studied.The results show that the optimum SLM process of 4J36 alloy is laser power of 250 W, scanning speed of 1000 mm/s, scanning distance of 0.1mm and layer thickness of 0.04mm.Under this process, the density of the sample is maximum of 99.53%, the tensile strength of the horizontal sample in formed state can reach 479 MPa, the elongation is 35%, the tensile strength of the vertical sample is 455 MPa, and the elongation is 38.5%.The strength of the sample in horizontal and vertical directions after solution+tempering+aging heat treatment is slightly lower, the elongation is improved and it reaches 44%for the horizontal sample and 48.5%for the vertical sample, which is better than that of the heat-treated forging.The low coefficient of thermal expansion (CTE) of 4J36 invar alloy is retained in samples in SLM formed and heat treated states, and the CTE of the sample in formed state is negative below 100℃, and the CTE of the sample after heat treatment is negative below 70℃, which is lower than that of the traditional machining+heat treated parts.