Abstract: In order to study the influence of fiber laser process parameters on the shape and size of the penetration spot weld, the single factor test method was used to conduct the penetration spot welding under different laser power, wobble amplitude and welding time. The power density distribution of laser and the shape and size of the spot weld were analyzed. The results show that the power density distribution in fiber laser spot affects the shape and size of spot weld. With the increase of laser power, the shape of spot weld formed by non-oscillating Gaussian beam gradually changes from parabolic shape to bell shape, and the weld width, weld depth, depth-to-width ratio and fusion width ratio of spot weld increase accordingly. The wobble of light beam increases the interaction area between laser and material, changes the power density distribution and the shape and size of spot weld. With the increase of wobble amplitude, the shape of spot weld gradually changes from bell shape to bowl shape, and the weld depth and depth-to-width ratio of spot weld gradually decrease while the fusion width ratio increases. Since the laser power density is basically unchanged, the welding time has little effect on the shape of spot weld. With the increase of welding time, the weld depth and weld width of spot weld gradually increase, but the depth-to-width ratio remains roughly the same.