A steady-state model of the coaxial parallel-type drive system is established to discuss the matching relations between the drive system and the dynamic load of the compressor. In order to improve energy conversion efficiency, this paper raises a torque control model, establishes the optimization scheme of the drive system and puts forward the switching law of the Hybrid-power Gas Engine Heat Pump (HPGHP). In addition, a new method of transmission ratio design is put forward to optimize the power matching of the drive system based on the load model of probability distribution. The simulation results show that the transmission ratios are respectively 3.2, 2 and 1.5 in three modes. At last, the energy management scheme of battery packs has been established. The results show that the state of the charge (SOC) can keep constant in one cycle when the ratio between the Mode L operation time and the Mode C operation time is about 1.38. And the variation range of SOC depends on the operation time of Mode D in one cycle. (C) 2013 Elsevier Ltd. All rights reserved.