A method for controlling a multi-split air conditioner, wherein the multi-split air conditioner comprises at least two outdoor units, each outdoor unit comprises a plurality of compressors, and the at least two outdoor units constitute an outdoor unit system, the method comprising, at the multi-split air conditioner: detecting whether a degree of superheat of each outdoor unit meets a target requirement; characterized in that: when the degree of superheat of each outdoor unit meets the target requirement, determining whether a difference between an average exhaust temperature of each outdoor unit and an average exhaust temperature of the outdoor unit system reaches a preset value, wherein the average exhaust temperature of each outdoor unit is the average of the exhaust temperatures of all compressors in each outdoor unit, and the average exhaust temperature of the outdoor unit system is the average of the average exhaust temperatures of each outdoor units; when the difference between the average exhaust temperature of each outdoor unit and the average exhaust temperature of the outdoor unit system reaches the preset value, comparing the average exhaust temperature of each outdoor unit with the average exhaust temperature of the outdoor unit system; controlling an electronic expansion valve to operate according to a result of comparing the average exhaust temperature of each outdoor unit with the average exhaust temperature of the outdoor unit system, to enable the average exhaust temperature of each outdoor unit to approximate to the average exhaust temperature of the outdoor unit system. detecting whether a degree of superheat of each outdoor unit meets a target requirement; characterized in that: when the degree of superheat of each outdoor unit meets the target requirement, determining whether a difference between an average exhaust temperature of each outdoor unit and an average exhaust temperature of the outdoor unit system reaches a preset value, wherein the average exhaust temperature of each outdoor unit is the average of the exhaust temperatures of all compressors in each outdoor unit, and the average exhaust temperature of the outdoor unit system is the average of the average exhaust temperatures of each outdoor units; when the difference between the average exhaust temperature of each outdoor unit and the average exhaust temperature of the outdoor unit system reaches the preset value, comparing the average exhaust temperature of each outdoor unit with the average exhaust temperature of the outdoor unit system; controlling an electronic expansion valve to operate according to a result of comparing the average exhaust temperature of each outdoor unit with the average exhaust temperature of the outdoor unit system, to enable the average exhaust temperature of each outdoor unit to approximate to the average exhaust temperature of the outdoor unit system. when the degree of superheat of each outdoor unit meets the target requirement, determining whether a difference between an average exhaust temperature of each outdoor unit and an average exhaust temperature of the outdoor unit system reaches a preset value, wherein the average exhaust temperature of each outdoor unit is the average of the exhaust temperatures of all compressors in each outdoor unit, and the average exhaust temperature of the outdoor unit system is the average of the average exhaust temperatures of each outdoor units; when the difference between the average exhaust temperature of each outdoor unit and the average exhaust temperature of the outdoor unit system reaches the preset value, comparing the average exhaust temperature of each outdoor unit with the average exhaust temperature of the outdoor unit system; controlling an electronic expansion valve to operate according to a result of comparing the average exhaust temperature of each outdoor unit with the average exhaust temperature of the outdoor unit system, to enable the average exhaust temperature of each outdoor unit to approximate to the average exhaust temperature of the outdoor unit system.