When aircraft laser paint is removed,the aluminum alloy substrate protection and paint removal efficiency are closely related to the material damage threshold,and the change of the laser defocus will directly change the material damage threshold and the paint removal efficiency.The ISO 11254 1 on 1 laser damage threshold test method is adopted to study the damage threshold of aluminum alloy and paint at different defocusing amounts.The two dimensional and three dimensional morphologies of the laser single pulse spot are analyzed,and the theoretical value and the actual value are compared.The diameter and depth of the damage craters at different defocusing amounts were verified.The results show that with the increase of the laser defocus,the spot area increases while the material damage threshold decreases,which can effectively improve the energy utilization and paint removal efficiency.The actual single pulse action of the material crater depth decreases with the increase of the defocus,and the area increases.The theoretical and measured values of crater depth,crater diameter show a good correlation,and the errors are explained from the perspective of the action mechanism of laser materials.