The ambient air dehumidification needs cooling down the air temperature in conventional heat pump dehumidification system. However, it decreased the temperature of hot air to the grain dryer, which reduced rice drying rate and increased energy consumption at the same time. A heat pipe heat exchanger was installed on the two sides of evaporator of heat pump dehumidification system, which was used for pre-cooling and pre-heating of ambient air respectively, so that dehumidifying capacity can be enhanced and the hot air temperature can be increased. Experiential results showed that with heat pipe in the system, the energy consumption of dehumidification were reduced by 9.6%~28.4% when air relative humidity was 60%~78% at 27℃. Meanwhile, the results demonstrated that dehydrating 1kg water from rice consumed 1560kJ energy when inlet air with relative humidity of 80.2% at 26.2℃, and saved 18.2% of energy compared with traditional heat pump dehumidification system.