A method for determining a set indoor temperature for an air conditioner, characterized by comprising: obtaining two or more indoor ambient temperatures at a set time interval within a set duration; determining whether an absolute value of a difference between every two adjacent indoor ambient temperatures in the two or more indoor ambient temperatures is greater than or equal to a set fluctuation amplitude threshold; if there is a set number of absolute values, among absolute values of the difference between every two adjacent indoor ambient temperatures in the two or more indoor ambient temperatures, and greater than or equal to the set fluctuation amplitude threshold, then determining that the fluctuation in the indoor ambient temperatures within the set duration reaches the set fluctuation amplitude threshold; if the fluctuation reaches the set fluctuation amplitude threshold, obtaining a temperature of a constant temperature space required by a user to function as a first constant temperature, and obtaining an outdoor ambient temperature and an outlet air temperature of the air conditioner; calculating a thermal load of a building according to the first constant temperature and the outdoor ambient temperature, and calculating a quantity of heat production of the air conditioner according to the first constant temperature and the outlet air temperature of the air conditioner; determining whether an absolute value of a difference between the first quantity of heat production of the air conditioner and the first thermal load of the building is less than or equal to a set load threshold; if the absolute value of the difference between the first quantity of heat production of the air conditioner and the first thermal load of the building is less than or equal to the set load threshold, then determining that the first constant temperature of the constant temperature space required by the user, which is related to both the first quantity of heat production of the air conditioner and the first thermal load of the building, is the set indoor temperature; if the absolute value of the difference between the first quantity of heat production of the air conditioner and the first thermal load of the building is greater than the set load threshold, then re-determining a second quantity of heat production of the air conditioner and a second thermal load of the building in an environment where the air conditioner is arranged, and re-determining the set indoor temperature based on an iterative method and according to a re-determined second quantity of heat production of the air conditioner and a re-determined second thermal load of the building in the environment where the air conditioner is arranged. obtaining two or more indoor ambient temperatures at a set time interval within a set duration; determining whether an absolute value of a difference between every two adjacent indoor ambient temperatures in the two or more indoor ambient temperatures is greater than or equal to a set fluctuation amplitude threshold; if there is a set number of absolute values, among absolute values of the difference between every two adjacent indoor ambient temperatures in the two or more indoor ambient temperatures, and greater than or equal to the set fluctuation amplitude threshold, then determining that the fluctuation in the indoor ambient temperatures within the set duration reaches the set fluctuation amplitude threshold; if the fluctuation reaches the set fluctuation amplitude threshold, obtaining a temperature of a constant temperature space required by a user to function as a first constant temperature, and obtaining an outdoor ambient temperature and an outlet air temperature of the air conditioner; calculating a thermal load of a building according to the first constant temperature and the outdoor ambient temperature, and calculating a quantity of heat production of the air conditioner according to the first constant temperature and the outlet air temperature of the air conditioner; determining whether an absolute value of a difference between the first quantity of heat production of the air conditioner and the first thermal load of the building is less than or equal to a set load threshold; if the absolute value of the difference between the first quantity of heat production of the air conditioner and the first thermal load of the building is less than or equal to the set load threshold, then determining that the first constant temperature of the constant temperature space required by the user, which is related to both the first quantity of heat production of the air conditioner and the first thermal load of the building, is the set indoor temperature; if the absolute value of the difference between the first quantity of heat production of the air conditioner and the first thermal load of the building is greater than the set load threshold, then re-determining a second quantity of heat production of the air conditioner and a second thermal load of the building in an environment where the air conditioner is arranged, and re-determining the set indoor temperature based on an iterative method and according to a re-determined second quantity of heat production of the air conditioner and a re-determined second thermal load of the building in the environment where the air conditioner is arranged.