To suppress the co-channel interference between cellular users and vehicle-to-vehicle (V2V) users in long-term-evolution (LTE) V2V communication system, an optimal power control scheme for energy efficiency (EE) maximization is presented with imperfect channel state information. In the scheme, the characteristics of time varying vehicular communication are described by the variation of communication distance between V2V users, and the co-channel interference of LTE-V2V communication system is modeled by stochastic geometry. Meanwhile, the feasible region of V2V users’ transmission power is obtained under the constraint of guaranteeing outage probability of cellular users and maximizing transmission power of V2V users. Further, the EE maximization target function of V2V users is formulated to solve the optimal power of V2V users. Numerical results show that the average sum rates can be maximized by adjusting the access density of V2V users and the EE of the proposed scheme can be improved in comparison with that of the previous maximum transmit power allocation scheme under different maximum communication distances of V2V users.