Optimisation of the parameters of the selective laser melting process based on the variation of the thermal behaviour of the melt pool through numerical simulation is an effective means of improving the quality of the formed parts. So, a fully parametric finite element analysis model of the temperature field of the selective laser melting process for IN738LC alloy was developed in the APDL language of ANSYS, and the heat source model was calibrated by single melt channel forming experiments. The results show that: with the increase of laser power or the decrease of scanning speed, the linear energy density absorbed by the powder increases, the maximum temperature of the melt pool centre increases, the molten metal volume increases, and the melt channel morphology evolves from irregular intermittent to regular continuous long strip; with the increase of scanning speed or the decrease of laser power, the linear energy density absorbed by the powder decreases, the melt flow capacity decreases, and the melt pool width and The FEM simulations are in good agreement with the experimental results. When the laser power is 270 W and the scanning speed is 1150 mm/s, the single melt channel has a continuous and good shape with few defects.