The rapid development of Unmanned Aerial Vehicle(UAV) based communication technology and the rapid growth of intelligent vehicle networking application promote the emergence and development of UAV assisted vehicle networking system. In UAV assisted vehicle networking system, how to save energy and maximize system performance is significant for nodes with limited energy. This paper mainly considers how to choose the optimal communication network link to maximize energy efficiency in the process of UAV assisted vehicle network communication. Firstly, a mixed integer programming model is established for link selection in communication networks. Then a network transmission link optimization algorithm in terms of energy efficiency maximization is proposed to obtain the optimal transmission link and the corresponding energy allocation. Finally, the effectiveness of the proposed algorithm is verified by numerical simulation.