Finite element software ANSYS is used to simulate the temperature field of the selective laser melting of Al Si10 Mg powder.Considering the characteristics of the thermophysical property of the material and the laser energy absorption rate varying with temperature, the laser heat source is regarded as a three-dimensional Gaussian heat source for moving loading on the powder bed.During the loading process of the heat source,the conversion of the properties of the material from the powder state to the solid state is realized in real time. The effects of the laser power,scanning speed and scanning interval on the thermal behavior of the powder bed are studied. The results show that the maximum temperature,size and cooling rate of the molten pool increase as the laser power increases. The maximum temperature and size of the molten pool decrease as the scanning speed increases,however,the cooling rate of the molten pool increases as the scanning speed increases. The scanning interval has little effect on the maximum temperature,size and cooling rate of the molten pool,but too large scanning interval is likely to cause hole defects.