Abstract: To reduce the energy consumption and improve economic performance of freeze-drying, a cascade system and a two-stage compression heat pump system for freeze-dryers, in which R600a/R290 and R290 served as work fluids respectively, have been investigated. The analyses on the performance of the two systems were conducted through variation of the temperature in the intermediate heat exchanger, heating platen and vapor condenser. The results show that the two systems are both feasible to freeze-dryer. Under the operational conditions in convention, the cascade heat pump system is slightly superior to the two-stage compression system.