Abstract: The power transmitting capacity of existing single range hydro-mechanical transmission cannot meet high power requirement of heavy duty vehicle. A new type of dual mode compound power split hydro-mechanical transmission was developed, based on the principle of input split and output split types of hydro-mechanical transmission(HMT). Qausi-steady state equations were provided with parameters of a certain vehicle. By the equations, the characteristics of speed ratio, output torque and the power flow were analyzed. The scheme took the advantages of both types of HMT, including good starting performance and power flow characteristics, and the wording range of hydraulic units were improved. It provides a platform for energy saving transmission and is of a promising future as well.