This paper presents a new method of laser focusing used in the process of direct laser fabrication. The hollow laser beam is achieved by transmission and conversion, which is studied by modeling and analysis in this paper. The defocus distance Z must be regulated in order to fabricate clad layers with good quality. The relationship between laser focal spot and the defocus distance was investigated. The focusing laser was solid when the absolute value of Z was equal to or smaller than while hollow on the other focal planes with different defocus distances, and the diameter of the minimum focusing spot is .