A carbon dioxide refrigeration system comprising a compressor, a condenser, a liquid reservoir, a gas-liquid separator and an evaporator which are connected in a listed sequence; wherein, a suction assembly is arranged between the compressor and the condenser, the suction assembly is in communication with the liquid reservoir or a gas-liquid separator, the gas-liquid separator is arranged between the condenser and the liquid reservoir, and the suction assembly is configured to suck carbon dioxide gas in the liquid reservoir or the gas-liquid separator back into a pipeline between the compressor and the condenser, characterised in that the condenser is a flash-evaporation condenser, the flash-evaporation condenser comprises a housing, a negative-pressure fan, a heat exchange device and a liquid atomization device, wherein the negative-pressure fan is arranged on the housing, the negative-pressure fan is configured to form a negative-pressure environment inside the housing, the liquid atomization device and the heat exchange device are arranged in the housing, the liquid atomization device is configured to spray an atomized liquid into the housing, and the atomized liquid evaporates into vapor in the negative-pressure environment to completely condense and liquefy a carbon dioxide medium in the heat exchange device, a first static pressure chamber is formed between the negative-pressure fan and the heat exchange device, a second static pressure chamber is formed between the liquid atomization device and the heat exchange device, the negative-pressure fan is configured to form a negative-pressure environment in the second static pressure chamber, and the liquid atomization device is configured to spray the atomized liquid into the second static pressure chamber to evaporate the atomized liquid into vapor; and the flash-evaporation condenser comprises a pressure regulating device, a gas inlet of the pressure regulating device is arranged outside the housing, an air outlet of the pressure regulating device is arranged inside the housing, a regulating air flow is sent into the housing by means of the pressure regulating device to promote flow of the vapor in the housing and form an aerosol in the housing; or the pressure regulating device is one or more fans, and the one or more fans are arranged close to the liquid atomization device; or the pressure regulating device is a negative-pressure fan connected to the housing through a vapor circulation pipeline. the condenser is a flash-evaporation condenser, the flash-evaporation condenser comprises a housing, a negative-pressure fan, a heat exchange device and a liquid atomization device, wherein the negative-pressure fan is arranged on the housing, the negative-pressure fan is configured to form a negative-pressure environment inside the housing, the liquid atomization device and the heat exchange device are arranged in the housing, the liquid atomization device is configured to spray an atomized liquid into the housing, and the atomized liquid evaporates into vapor in the negative-pressure environment to completely condense and liquefy a carbon dioxide medium in the heat exchange device, a first static pressure chamber is formed between the negative-pressure fan and the heat exchange device, a second static pressure chamber is formed between the liquid atomization device and the heat exchange device, the negative-pressure fan is configured to form a negative-pressure environment in the second static pressure chamber, and the liquid atomization device is configured to spray the atomized liquid into the second static pressure chamber to evaporate the atomized liquid into vapor; and the flash-evaporation condenser comprises a pressure regulating device, a gas inlet of the pressure regulating device is arranged outside the housing, an air outlet of the pressure regulating device is arranged inside the housing, a regulating air flow is sent into the housing by means of the pressure regulating device to promote flow of the vapor in the housing and form an aerosol in the housing; or the pressure regulating device is one or more fans, and the one or more fans are arranged close to the liquid atomization device; or the pressure regulating device is a negative-pressure fan connected to the housing through a vapor circulation pipeline.