Laser stir welding is used herein to perform butt welding of 7075 aluminum alloy and carbon fiber reinforced thermoplastic (CFRTP), and the effect of the welding process parameters on the joint strength is analyzed. The mechanical properties of the welded joint are tested, and the factors affecting the joint strength and the failure mode of the joint are analyzed. Results show that the welding speed has the greatest influence on the joint strength, followed by the defocusing amount, laser power, stirring amplitude, stirring frequency, and clamp pressure. Under optimal parameters, the joint strength is 11.7 MPa. In this case, the fracture of the joint occurs in the surface layer of CFRTP, and the failure mode of the joint is the tearing of the CFRTP matrix. The temperature change law of the joint during the welding is measured, and the strength of the joint is reduced if the temperature is extremely high or low. Proper welding speed can prolong the high temperature time of the joint welding, increasing the joint strength.