<p>This study aims to introduce the heat source models in the traditional selective laser melting (SLM) process and, focusing on the setting of process parameters, establish two heat source models, namely a surface laser heat source model and a volumetric laser heat source model. Through experiments and numerical simulations, the effect of different heat source models on the temperature and flow fields, as well as the influence of different process parameters such as laser power, scanning speed, and scanning distance on the molten pool state and forming quality are investigated. The results indicate that unlike the traditional Gaussian laser heat source model, the Gaussian volumetric model takes into account the absorption of laser beam energy in the depth direction. Also, by comparing the results, it is found that the volumetric heat source model has a better fit with the experimental results and smaller errors. Meanwhile, significant differences are found in the temperature gradient and cooling rate between the two heat source models. Therefore, the volumetric heat source model is adopted in the simulation to verify the influence of process parameters on the forming quality in selective laser melting. On the other hand, the results indicate that when the laser power is 400W or the scanning speed is 0.8m/s, the energy density is higher, the cooling rate is accelerated, and the grains are refined. In particular, when the laser power reaches 400W, the maximum temperature of the molten pool reaches the boiling point of the metal material. At this time, the molten pool is affected by the vapor recoil pressure, fluctuates violently, and even produces splashing phenomena, resulting in a decrease in the density of the formed part and poor forming quality. In addition, when the laser power is 100W or the scanning speed is 1.4m/s, the laser energy density input into the molten pool is small, and the metallurgical bonding effect between adjacent molten tracks is poor. The scanning spacing is found to have little effect on the energy density of the molten pool and thus little effect on the forming porosity. However, with the increase of scanning spacing, the overlapping rate decreases and the flatness of the molten track deteriorates. This may then affect the powder spreading between layers, cause the accumulation of interlayer defects, and further affect the surface roughness.</p>