Cascade refrigerating system

The invention discloses a cascade refrigerating system, and particularly relates to the technical field of refrigerating systems. According to the cascade refrigerating system, a novel environment-friendly organic working medium is adopted for carrying out waste heat recycling on an absorption refrigeration system, and the utilization rate of waste heat is increased. The cascade refrigerating system comprises an absorption refrigeration subsystem and a compression refrigerating subsystem. A waste heat pipeline of the absorption refrigeration subsystem is connected with a generation fractionator, and the output end of the generation fractionator is connected with a solution heat exchanger and an air cooling condenser, and the air cooling condenser is connected with an expansion valve. The output end of the expansion valve is connected with an evaporation condenser, and the evaporation condenser is connected with an air cooling absorber. The output end of the air cooling absorber is connected with the generatio