In order to reduce thermal stress and crack of clad layer in laser cladding process, a method through changing power density distribution of laser beam was presented. A thermal-mechanical coupling finite element model of laser cladding by using uniform shape and convex shape laser spot was established. The results show that laser cladding with uniform shape spot has a typical character of quick heating and cooling rate as the conventional laser manufacturing. However, laser cladding with convex shape beam could preheat and slow cooling rate of sample to some extent, and reduce the temperature gradient between the clad area and non-clad zone. In addition, the thermal stress of clad layer with convex shape laser beam is lower than the uniform shape laser spot dose, so it can effectively reduce crack of the clad layer.