A refrigeration system, including: a control module, a chiller, a natural cold source, a cooling pool and an intermediate heat exchanger; wherein the chiller includes a compressor, a condenser and an evaporator; a water outlet of the evaporator and a water outlet of the natural cold source are respectively connected to an water inlet of the intermediate heat exchanger and a water inlet of the evaporator and a water inlet of the natural cold source are respectively connected to a water outlet of the intermediate heat exchanger; a liquid inlet of the intermediate heat exchanger is connected to a liquid outlet of the cooling pool, and a liquid outlet of the intermediate heat exchanger is connected to a liquid inlet of the cooling pool; characterized in that, the control module is configured to obtain a lowest temperature T min, a highest temperature T max within one day of a place where the refrigeration system is located and a preset target discharge water temperature of the evaporator T o; and the control module is configured to determine whether or not to start the chiller or the natural cooling source according to the T min, T max and T o: if T o < T min, the chiller is started to cool a liquid in the cooling pool; if T o > T max, the natural cold source is started to cool the liquid in the cooling pool; if T min ≤T o ≤T max, an actual inlet water temperature T i at the water inlet of the intermediate heat exchanger is collected every set time period for determining whether or not the actual inlet water temperature T i satisfies T i ≥ T o - a set value, wherein the set value > 0; if T i ≥ T o - the set value, the chiller is started to cool the liquid in the cooling pool; if T i < T o - the set value, the natural cold source is started to cool the liquid in the cooling pool. intermediate heat exchanger; wherein the chiller includes a compressor, a condenser and an evaporator; a water outlet of the evaporator and a water outlet of the natural cold source are respectively connected to an water inlet of the intermediate heat exchanger and a water inlet of the evaporator and a water inlet of the natural cold source are respectively connected to a water outlet of the intermediate heat exchanger; a liquid inlet of the intermediate heat exchanger is connected to a liquid outlet of the cooling pool, and a liquid outlet of the intermediate heat exchanger is connected to a liquid inlet of the cooling pool; characterized in that, the control module is configured to obtain a lowest temperature T min, a highest temperature T max within one day of a place where the refrigeration system is located and a preset target discharge water temperature of the evaporator T o; and the control module is configured to determine whether or not to start the chiller or the natural cooling source according to the T min, T max and T o: if T o < T min, the chiller is started to cool a liquid in the cooling pool; if T o > T max, the natural cold source is started to cool the liquid in the cooling pool; if T min ≤T o ≤T max, an actual inlet water temperature T i at the water inlet of the intermediate heat exchanger is collected every set time period for determining whether or not the actual inlet water temperature T i satisfies T i ≥ T o - a set value, wherein the set value > 0; if T i ≥ T o - the set value, the chiller is started to cool the liquid in the cooling pool; if T i < T o - the set value, the natural cold source is started to cool the liquid in the cooling pool. if T o < T min, the chiller is started to cool a liquid in the cooling pool; if T o > T max, the natural cold source is started to cool the liquid in the cooling pool; if T min ≤T o ≤T max, an actual inlet water temperature T i at the water inlet of the intermediate heat exchanger is collected every set time period for determining whether or not the actual inlet water temperature T i satisfies T i ≥ T o - a set value, wherein the set value > 0; if T i ≥ T o - the set value, the chiller is started to cool the liquid in the cooling pool; if T i < T o - the set value, the natural cold source is started to cool the liquid in the cooling pool. if T i ≥ T o - the set value, the chiller is started to cool the liquid in the cooling pool; if T i < T o - the set value, the natural cold source is started to cool the liquid in the cooling pool.