The invention discloses an energy-saving refrigeration system for an ultralow-temperature freezer. The refrigeration system comprises a compressor (1), a condenser (2) and a heat exchanger (3). An exhaust pipe (4) is connected between the compressor (1) and the condenser (2), and an air return pipe (5) is connected between the compressor (1) and the heat exchanger (3); a drying filter (7) and a gas-liquid-oil separator (6) are connected between the condenser (2) and the heat exchanger (3); the gas-liquid-oil separator (6) comprises an upper shell (61) and a lower shell (62), and a wire ball filter (63) is arranged in the upper shell (61); and a gas-liquid-oil leading-in pipe (64) is arranged on the lower shell (62), a bend section (65) is arranged at one end of the gas-liquid-oil leading-in pipe (64), and a fine-mesh filter screen (66) is arranged below the bend section (65). The refrigeration system can improve the separation effect, and has the advantages that the energy consumption is low, the refrigerating effect is good, energy is saved, the cyclic utilization rate is high, and using is convenient.