A pre-cooling device for cryotherapy, comprising a gas inlet port, at least three vent branches, a single-stage-compression auto-cascade refrigeration system assembly and a pressure regulating assembly, wherein the gas inlet port communicates with a gas inlet end of the pressure regulating assembly; a gas outlet end of the pressure regulating assembly is connected to gas inlet ends of the at least three vent branches respectively; a gas inlet end of a cryoprobe connector for a cryoprobe is connected to gas outlet ends of the at least three vent branches respectively; the single-stage-compression auto-cascade refrigeration system assembly comprises at least three-stage refrigeration cycles; for at least some of the refrigeration cycles, a refrigeration temperature thereof is lower than that of the previous stage refrigeration cycle; each refrigeration cycle is capable of exchanging heat with a gas flowing in the corresponding vent branch to pre-cool the gas flowing in this vent branch; each vent branch is provided with a branch control member configured to control connection and disconnection of this vent branch; and the pressure regulating assembly is configured to control a pressure of the gas outlet end of the pressure regulating assembly, the pressure of the gas outlet end of the pressure regulating assembly is associated with a vent branch to be pre-cooled, and for at least two vent branches, the gas outlet end of the pressure regulating assembly has different pressures during pre-cooling; wherein the pressure regulating assembly is configured to control the pressure of the gas outlet end of the pressure regulating assembly according to first pressure information and/or second pressure information, wherein the first pressure information represents a pressure of a gas inlet end of the cryoprobe connector, and the second pressure information represents a pressure of the gas inlet end of the pressure regulating assembly; the pressure regulating assembly comprises a proportional decompression valve and a controller; the gas inlet end of the cryoprobe connector is connected with a first pressure sensor configured to detect the first pressure information; a gas inlet end of the proportional decompression valve is connected with a second pressure sensor configured to detect the second pressure information; a gas outlet end of the proportional decompression valve is connected with a third pressure sensor; and the controller is connected with the first pressure sensor, the second pressure sensor and the third pressure sensor respectively, and is configured to control the proportional decompression valve according to information detected by the first pressure sensor, the second pressure sensor and the third pressure sensor. the single-stage-compression auto-cascade refrigeration system assembly comprises at least three-stage refrigeration cycles; for at least some of the refrigeration cycles, a refrigeration temperature thereof is lower than that of the previous stage refrigeration cycle; each refrigeration cycle is capable of exchanging heat with a gas flowing in the corresponding vent branch to pre-cool the gas flowing in this vent branch; each vent branch is provided with a branch control member configured to control connection and disconnection of this vent branch; and the pressure regulating assembly is configured to control a pressure of the gas outlet end of the pressure regulating assembly, the pressure of the gas outlet end of the pressure regulating assembly is associated with a vent branch to be pre-cooled, and for at least two vent branches, the gas outlet end of the pressure regulating assembly has different pressures during pre-cooling; wherein the pressure regulating assembly is configured to control the pressure of the gas outlet end of the pressure regulating assembly according to first pressure information and/or second pressure information, wherein the first pressure information represents a pressure of a gas inlet end of the cryoprobe connector, and the second pressure information represents a pressure of the gas inlet end of the pressure regulating assembly; the pressure regulating assembly comprises a proportional decompression valve and a controller; the gas inlet end of the cryoprobe connector is connected with a first pressure sensor configured to detect the first pressure information; a gas inlet end of the proportional decompression valve is connected with a second pressure sensor configured to detect the second pressure information; a gas outlet end of the proportional decompression valve is connected with a third pressure sensor; and the controller is connected with the first pressure sensor, the second pressure sensor and the third pressure sensor respectively, and is configured to control the proportional decompression valve according to information detected by the first pressure sensor, the second pressure sensor and the third pressure sensor.