The heat pump unit absorbs the heat from the air outside the drying room and transfers it to the drying room. The dried hot air circulates through the lost foam model, taking away water. The high humidity hot air is discharged through the return air pipeline to the heat exchanger and heat recovery evaporator of the heat pump drying system. The temperature of the hot and humid air drops below the dew point temperature, and water is released and discharged. Finally, achieve continuous drying of the model.