In this paper, we introduce the laser stir welding method to reduce the welding defect of laser heating to aluminum alloy during the laser welding of carbon fiber reinforced thermal polymers (CFRTP)/aluminum alloy and improve the mechanical properties of welded joints during the jointing process. With the same laser power and welding speed, the jointing strength of this method is 3.25 times of that of the traditional linear welding method. Moreover, the bubble defect in laser stir welding is significantly reduced, and a good welding morphology is obtained. Further, the temperature field in the laser stir welding of the CFRTP/aluminum alloy is simulated to study the mechanism of laser stir welding in CFRTP/aluminum alloy. The results show that the temperature on the surface of aluminum alloy changes in the form of a non-equal amplitude oscillation. Two peaks are observed, and laser stir welding can reduce the welding defect owing to these peaks, amongst other reasons. The weld depth and width are calculated, and the error is within 9.87%.