To solve the problem that it is difficult to accurately reflect the temperature change in laser transmission welding process by experimental methods, this paper takes the polyarylsulfone (PASF) laser transmission welding based on zinc powder absorbent as the research object, and established a three-dimensional finite element model reflecting the welding process in COMSOL. The accuracy of the model is verified by comparing the weld width obtained by simulation with the actual weld width. The effect of different welding parameters (laser power, welding speed and zinc powder absorbent level) on the temperature field was analyzed. The results show that with the increases of laser power, the maximum temperature increases. With the increases of welding speed, the maximum temperature decreases. With the increases of zinc powder absorbent level, the maximum temperature increases but the rate of heating is falling, and begins to decrease after reaching the maximum value.