A multi-connection air conditioning system and a method for calculating a heat exchange amount thereof includes a plurality of indoor units, and the method includes: obtaining a total heat exchange amount of the multi-connection air conditioning system; obtaining inlet air temperature of each indoor unit; obtaining a two-phase saturation temperature of each indoor unit; obtaining an air supply volume of each indoor unit; obtaining a heat exchange area of each indoor unit; and calculating a heat exchange amount of each indoor unit according to the total heat exchange amount of the multi-connection air conditioning system, the inlet air temperature of each indoor unit, the two-phase saturation temperature of each indoor unit, the air supply volume of each indoor unit, and the heat exchange area of each indoor unit. Thus the user can monitor the heat exchange amount of each indoor unit so that they can be managed with separate targets.