Series-parallel Plug-In Hybrid Electric Vehicle combine the advantages of series and parallel configurations and have been used in China. However, battery degradation in series-parallel Plug-In Hybrid Electric city bus applications still need to be investigated. In this paper, a simulation model is developed to simulate a series-parallel Plug-In Hybrid Electric city bus. The simulation model was validated experimentally and shown to agree well with the real system. Additionally, a semi-empirical battery life model was also developed and validated to estimate the battery degradation. According to the simulation model and battery life model, the impact of different control strategies for series-parallel Plug-In Hybrid Electric city buses on battery degradation was investigated. The simulation results showed that series-parallel Plug-In Hybrid Electric city buses with the Maximum Efficiency Control Strategy for series mode and Power Follower Control Strategy for parallel mode reduced battery degradation significantly. (C) 2016 Elsevier Ltd. All rights reserved.