The influences of three typical stretch forming trajectories on stretch forming of melon shaped bottom for aluminum alloy tank were analyzed by the finite element analysis software ABAQUS, and the experiment verification was carried out. The results show that through the stretch forming trajectory of first covering and then stretching, the forming force cannot be effectively transferred to the forming area and concentrated in the fillet of die, the wall thickness at fillet is 6.7 mm, and the wall thicknesses of the rest areas remain unchanged, which is 6.9-7.0 mm. Therefore, the strain distribution of part is not uniform, and the forming results is poor. However, the stretch forming trajectory of first stretching and then covering is used, the part produces large deformation, and the transition fillet has the risk of fracture in forming process, namely, the minimum wall thickness is 6.2 mm and the thinning rate is 11.5%. Furthermore, by the stretch forming trajectory of covering and stretching at the same time, the variation trend of strain distribution for part is relatively smooth, the wall thickness distribution is more uniform, and the wall thickness of part is 6.6-6.8 mm.