Electro-mechanical transmission (EMT), with power distribution strategy as its core technology, stands for the developing orientation of the heavy vehicles' transmission, which is able to fulfill power, fuel economy and electricity demand of the vehicles. Furthermore, the demand power prediction has significant meaning for the improvement of the control strategy performance. In this paper, the mechanical and electrical power balance equations were established according to the split and convergence characteristics of the power coupling mechanism. The power demand of the EMT is predicted through combination of the fixed-gain prediction algorithms and the input that driver's desired speed during the vehicle driving cycle. Then the optimal power distribution strategy based on power prediction algorithm is achieved. Moreover, the optimal allocation pattern of the engine and motors is proposed. The rationality of control strategy is verified by the forward simulation results, which shows the new strategy based on the demand power prediction has better power performance and fuel economy than the traditional rule-based one.