Abstract: The performance and key technology of the two-stage compression system of the heat pump dryer are described in this paper.Combining the two-stage compression and frequency conversion technology, a two-stage compression variable frequency pump dryer system for extreme cold and extreme heat areas was developed. The experiment results show that the low frequency operation of the heat pump dryer at-20℃, or even-25℃, and the low frequency operation in summer and winter can achieve the goal of stable operation all year round in summer and winter. The experimental analysis and benefit comparison show that the multi-purpose, wireless monitoring and wide range of intelligent heat pump dryers, and the promotion and application of this equipment will effectively improve the reduction of drying of agricultural products, reduce the cost, improve quality, efficiency, energy saving, environmental protection and other work benefits.