In order to improve the welding quality of 6061 aluminum alloy, we utilize the nanosecond pulse laser to pretreat 6061 aluminum alloy, and then observe its surface morphology with scanning electron microscope. The contents and distribution of oxygen at different laser parameters are studied by line analysis and surface analysis. In order to verify the laser cleaning effect, we carry out the welding experiments. The research results show that the optimal laser pretreatment parameters is cleaning the aluminum alloy surface 5 times with 15 W pulse laser power, which makes the mass fraction of oxygen is 3.23%, and oxygen is mainly distributed in the overlapping place of the spot. The weld is smooth and uniform,and without any obvious defects after pretreatment with laser optimum process parameters. The lower surface oxygen content, the higher weld quality. The small amount of oxygen distributed around the spot does not affect the welding quality.