To satisfy the recent growth of mobile data usage, small cells are recommended to deploy into conventional cellular networks. However, the massive backhaul traffic is a troublesome problem for small cell networks, especial in wireless backhaul transmission links. In this paper, backhaul traffic models are first presented considering the Gauss-Markov mobile models of mobile stations (MSs) in small cell networks. Furthermore, an energy efficiency model of small cell backhaul networks with Gauss-Markov mobile models has been proposed. Numerical results indicate that the energy efficiency of small cell backhaul networks can be optimized by trade-off the number and radius of small cells in cellular networks.