An energy balancing routing model and its solution algorithm in wireless sensor networks are proposed in this paper, taking all the following factors into consideration: link access, packet transmission energy consumption and the remaining energy in the nodes. Its objective is to balance the energy consumption and maximize the network lifetime. Firstly, a distributed dynamic routing tree building algorithm and a routing selection function of two neighbor nodes are proposed with the cross-layer method, which satisfied the nodes’ computing capabilities. Secondly, a bi-level programming model and its algorithm are presented to make the energy consumption of the network tend to equilibrium and maximize the network lifetime. A numerical example illustrates the validation of the proposed routing policy and the bi-level programming model.