This paper uses COMSOL finite element simulation software to numerically simulate the fusion forming process of the area laser exposure of a powder bed. The temperature field and flow field distribution law for this fusion formation process are obtained, and the surface tension and Marangoni effect are analyzed through the development of the flow and temperature fields. The effect of the force on the formation of the molten pool is investigated. The results show that compared with traditional laser powder bed fusion forming, area laser exposure powder bed fusion forming has a smaller peak flow rate and very small temperature gradient in the horizontal direction. The surface tension is the key factor in the formation of the molten pool and the main driving force for forming, while the resulting molten pool has less surface roughness.