The fuel tank is an important part of the fuel supply system. Leakage due to the cracking of fuel tank during the operation may lead to dangerous accidents. In order to ensure the strength of the fuel tank in use, the finite element method is applied to analyze the structural strength of the fuel tank in the process of fuel tank design. Taking the braking process of the fuel tank with half tank fuel as an example, the deformation and stress of the fuel tank are calculated by finite element method, and the weak links of the fuel tank are found out, which is consistent with the actual use. Aiming at the weakness of the existing fuel tank, some suggestions for structural improvement are put forward. The finite element analysis results show that the improved scheme is effective and feasible.