The utility model relates to an energy -conserving compressive refrigerating system, including compressor and knockout drum, its characterized in that: the refrigerant collection tank is connected via the cooler to the outlet line of compressor, the first entry of the first strand of connection sprayer of export of refrigerant collection tank, the second stock -traders' know -how is connected by first choke valve the entry of three -section entry knockout drum, the the second entrance of sprayer connects the export of one section entry pipeline of compressor, sprayer the entry of three -section entry knockout drum, the gas exports of three -section entry knockout drum connects the three -section entry of compressor, get into out -of -bounds user behind the first strand of first passageway that gets into first subcooler of the liquid phase export of three -section entry knockout drum after the heat transfer, get into two -stage process entry knockout drum after the second channel heat transfer of second stock -traders' know -how by the first subcooler of second choke valve entering, the gas exports of two -stage process entry knockout drum connects the two -stage process entry of compressor, one section user connection entry knockout drum out -of -bounds, the gas exports of one section entry knockout drum connects one section entry of compressor.