In vehicular edge network, the mobility of vehicles will have a great impact on the optimal placement of cache content. At the same time, if the vehicles that need to update the cache content are not selected properly, it will bring a large energy loss to base station(BS). Therefore, this paper first proposes a vehicle selection strategy, which determines which vehicles need to be updated by prioritizing the vehicles. Then, considering the mobility and randomness of vehicles, this paper presents an problem to minimize the average energy consumption of base stations BS. The problem is transformed into the maximization of monotonic submodular function under matroid constraint, and it can be solved by greedy algorithm. Finally, the experimental results verify the effectiveness of the scheme.