We have discussed the effect of the variation of target absorptance on the temperature distribution of the target before melting. The relationship of the target absoptance with time is derived. Based on this relationship and the actual shape of incident energy density which is a Gauss distribution, the relevant heat flow equation is set up. By using the finite difference method, heat flow equation under an appropriate boundary condition is solved. We have obtained the temperature distribution as function of time and location. At the same time, we have also discussed the physical picture of a relevant process in detail. Finally, we have studied the effect of the variation of absorptance and the distribution of incident energy density on the relevant process. The result shows that during the pulsed laser process, the variation of target absorptance has an important effect on the final simulation result. If this variation is neglected, a remarkable difference can be found between theoretical results and experimental data.