Based on the ANSYS "element birth and death technology",a three-dimensional finite element analysis model of multilayer laser cladding is established. The distribution law of temperature field of multilayer laser cladding is obtained,and the influence of preheating temperature on thermal cycle of laser cladding is analyzed. The experimental results show that the heating speed of the nodes parallel to the moving direction of the heat source is faster and the cooling speed is slower. For the nodes perpendicular to the moving direction of the heat source,the closer to the center of the cladding layer,the faster the heating speed and cooling speed.The temperature gradient of node in Y direction is greater than that in X direction. When the heat input remains constant,as the preheating temperature increases,the heating speed changes little,the peak temperature increases,and the residence time above the phase transition temperature stays longer,but the residence time at high temperature has little change. When the preheating temperature is 200 ℃,the t8/5 parameter is about 3.2 times of that without preheating,and the cracking tendency of the cladding can be reduced by preheating. The simulation results show that preheating can effectively reduce the coating stress.