Laser forming is a technique of using the energy from a laser beam to modify and adjust the curvature of sheet metals or hard materials. 2-dimention (2D) laser forming can reasonably accurately control bend angles with various materials. To advance this process further for realistic forming applications in a manufacturing industry, it is necessary to consider larger scale controlled 3-dimention (3D) laser forming. On the base of mechanism of 2D laser forming, the deformation mainly depends on the temperature gradient between upper and bottom surface of sheet metal. The work presented in this paper shows that the temperature field of using the spider scanning path to transform the thin square sheet to spherical dome by 3D laser forming. The explicit thermal analysis on 3D laser forming is shown in the article. This paper discusses the interaction between moving laser beam and sheet, the varied temperature field on the sheet during laser scanning. In order to give the verification on the results of simulation, the correlative experiment has progressed and the results of experiments are in accord with the simulation.