Pointing at the unfavorable conditions and improving the reliability of the drying system, a coupled application scheme of low-temperature heat pump(LTHP) and dry heat pump(DHP) is proposed, according to the principle of two stage compression refrigeration cycle. By using the exergy analysis model, the exergy loss of the heat, the mass diffusion of the drying medium and the dehumidification process were analyzed respectively to the drying system. With the LTHP at 20, 22, 24, 26, 28, 30℃ and closed, the experiment tests and calculates the exhaust temperature and energy consumption of the compressor of DHP, coefficient of performance and the thermodynamic perfect degrees. The drying time and energy consumption of the system were measured when the water content of wood was decreased by 1%, at different heating temperatures. The results show that:compared with shutting down the LTHP, the exhaust temperature of the drying heat pump is reduced by 16℃ at most, and all the performance coefficient of the heat pump is improved. By the increase of the temperature of the machine hall, the irreversibility of the system cycle increases, and the thermodynamic perfect degrees decreases gradually. After opening the LTHP, the maximum amount of heating load and the drying time of the DHP increases by 44% and decreases by 46%, respectively.