Abstract: An online energy management strategy was proposed based on Pontryagin's minimum principle for an extended range electric school bus and its principle to realize SOC sustaining was analyzed. A high-fidelity forward simulation model was built with component experimental data in the Matlab/Simulink environment. The simulation results show that, the proposed strategy is very robust in different driving cycles; and the fuel economy performance can be improved by up to 5.8% compared with the traditional on/off strategy.