An air volume regulation method for an air volume regulation device, the air volume regulation device comprising: a fan system provided in a cabinet air conditioner, an upper air outlet provided in an upper part of the cabinet air conditioner, a lower air outlet provided in a lower part of the cabinet air conditioner and a control system, wherein the fan system comprises a plurality of fans driven by motors respectively, and a port of each of the plurality of fans is communicated with a main air passage formed by at least a part of an air conditioner housing; and the control system is configured to control each of the plurality of fans to execute at least one operation of starting, stopping and power regulation, thereby regulating an outlet air volume, the air volume regulation method comprising: starting all fans or part of the fans according to an environmental temperature; maintaining or reducing a number of the fans which have run according to a rotating speed of each of the fans; and closing or opening the lower air outlet according to a running stage of the air conditioner; the method characterized in that: starting all the fans or part of the fans according to the environmental temperature comprises: detecting the environmental temperature; judging whether a temperature difference between the environmental temperature and a preset temperature is larger than a first threshold value or not; if the temperature difference is larger than the first threshold value, starting all the fans; if the temperature difference is not larger than the first threshold value and the environmental temperature does not exceed the preset temperature, starting all the fans; and if the temperature difference is not larger than the first threshold value and the environmental temperature exceeds the preset temperature, starting part of the fans. wherein the fan system comprises a plurality of fans driven by motors respectively, and a port of each of the plurality of fans is communicated with a main air passage formed by at least a part of an air conditioner housing; and the control system is configured to control each of the plurality of fans to execute at least one operation of starting, stopping and power regulation, thereby regulating an outlet air volume, the air volume regulation method comprising: starting all fans or part of the fans according to an environmental temperature; maintaining or reducing a number of the fans which have run according to a rotating speed of each of the fans; and closing or opening the lower air outlet according to a running stage of the air conditioner; the method characterized in that: starting all the fans or part of the fans according to the environmental temperature comprises: detecting the environmental temperature; judging whether a temperature difference between the environmental temperature and a preset temperature is larger than a first threshold value or not; if the temperature difference is larger than the first threshold value, starting all the fans; if the temperature difference is not larger than the first threshold value and the environmental temperature does not exceed the preset temperature, starting all the fans; and if the temperature difference is not larger than the first threshold value and the environmental temperature exceeds the preset temperature, starting part of the fans. detecting the environmental temperature; judging whether a temperature difference between the environmental temperature and a preset temperature is larger than a first threshold value or not; if the temperature difference is larger than the first threshold value, starting all the fans; if the temperature difference is not larger than the first threshold value and the environmental temperature does not exceed the preset temperature, starting all the fans; and if the temperature difference is not larger than the first threshold value and the environmental temperature exceeds the preset temperature, starting part of the fans.