In order to explore the morphology of molten pool and the distribution of temperature field in the process of laser additive manufacturing on the surface of aluminum alloy plate, a three-dimensional finite element model of fluid heat transfer was established. Considering the thermophysical properties of the material during processing and the change of laser absorption rate with temperature, the effects of laser power and scanning speed on the flow field and temperature field distribution of the molten pool were studied. The results show that in the process of processing, the morphology of the molten pool will be affected by gravity, recoil pressure and Marangoni effect. Larger laser power and lower scanning speed can make the molten pool have higher temperature and larger size, but it is easy to cause splashing of the metal liquid in the molten pool, which affects the processing quality of the material. Smaller laser power and higher scanning speed will lead to insufficient energy of the material to absorb the laser and cannot be fully melted, which is prone to spheroidization. When the laser power is set at 86 W and the scanning speed is set near 1300mm/s, the parts can obtain good forming quality. This study provides a certain theoretical and data reference for laser additive manufacturing of 6061 aluminum alloy.