The change of center of gravity (CG) of aircraft is influenced by fuel system greatly. In this paper, according to all of failure mode of fuel system 6 fuel transfer mode were discussed. Based on 6 fuel transfer mode, the models of CG of aircraft were established. The fuel system of military aircraft was token an example. The law of change of (CG) during fuel consumption was obtained. The influence of aircraft CG by Failure mode of fuel system was discussed. This paper lays foundation for the future study.