The dual-mode electro-mechanical transmission system for heavy duty vehicles is a power split hybrid system, which transmits engine power through mechanical and electrical power flow. Aiming at the precision of mechanical and electrical power distribution and the responding speed of electrical power supply, the electric power coordinated control strategy is proposed. Making use of quick response and accuracy control of motors, the strategy can realize the precise power distribution of engine and battery and supply steady electric power by coordinating the working state of generator and motor. The simulation results indicate that the actual power of battery will follow its target value in real time and the electric power will be supplied rapidly when it is needed. The electric power coordinated control strategy can achieve the precise distribution of mechanical and electrical power and the high responding speed of electrical power supply in complex dynamic control system.