In order to investigate the thermal accumulation effect on the properties of two build directions of 0° and 90° during the selective laser melting. Based on the ANSYS simulation of molten pool size and thermal accumulation effect, the mechanical properties of the two build-formed parts were explored experimentally, and the differences in melt pool size, density, XRD, microstructure and mechanical properties between 0° and 90° build directions were analyzed. Results show that the thermal accumulation of the vertical build-formed parts is higher than that of the horizontal build-formed parts under the same bulk energy density, which results in higher melt pool size and γ-phase content than that of the horizontal build-formed parts, and thus the difference in the densities and mechanical properties between the two build-formed parts. Due to the effect of heat accumulation, the γ-phase content of different forming parts of the vertical build forming parts changes.