An energy-saving control method for a vacuum freezing and drying combined device for a cascaded heat pump comprises the steps of: 1, according to requirements of a food drying technology, determining the temperature T1 of a heating medium entering heating division plates (8) of a drying chamber 2, according to vacuum degree requirements of the combined device and thickness changes of a frost layer on the surface of a water catcher (12) in the operation process of the combined device, determining a functional expression of the change of the evaporation temperature T5 of the water catcher (12) along with operation time t in the operation process of the combined device 3, according to the evaporation temperature T5 of the water catcher (12) in a low-pressure-stage refrigeration system and the condensation temperature T2 of a high-pressure-stage condenser (7), determining the high-pressure-stage evaporation temperature T3 of a condensation evaporator (10), and determining a functional expression of the change of the high-pressure-stage evaporation temperature T3 along with the evaporation temperature T5 and the condensation temperature T2 and 4, according to the functional expression of the evaporation temperature T5 of the water catcher (12) changing along with the operation time t, controlling the high-pressure-stage evaporation temperature T3 by adjusting the opening degree of a high-pressure-stage throttling valve and adjusting the rotation speed of a high-pressure-stage compressor. The method has the advantages: the evaporation temperature of the low-pressure-stage water catcher (12) can be dynamically adjusted according to the thickness changes of the frost on the surface of the water catcher (12), and the cascaded refrigeration system saves energy in operation.La présente invention concerne un procédé de commande déconomie dénergie pour un dispositif combiné de congélation et de séchage sous vide pour une pompe à chaleur en cascade comprenant les étapes suivantes
