Aiming at the process need of surface cleaning before aluminum alloy welding in the development of lightweight, the mechanism of fiber laser cleaning for aluminum alloy is investigated. Laser arrangement in laser cleaning is determined by analyzing the laser space and energy distribution parameters. Laser cleaning process experiment is conducted to study the influence of laser parameters on surface state, explore and optimize the oxide film stripping process. Two possible kinds of aluminum alloy oxide film stripping mechanism are proposed. The results of welding evaluation for cleaning parameters after optimization show that laser cleaning can improve the formation quality of the welding line and mechanical property of the joint, which verifies that the fiber laser cleaning can improve the quality of aluminum alloy joint. The research will promote the widespread application of high strength aluminum alloy joint in the manufacturing industry.