The purpose of the present study was to develop a method to forecast the capacity of air- conditioning (AC) systems based on the ENVLOAD index presented in relevant building regulations. This study firstly defined the standard buildings. Secondly, the maximum heat load was calculated by ETD, with the simulation of the energy consumption of air conditioning load dine by eQuest. A regression analysis was then performed on these samples to establish ACSc forecasting equations for the buildings AC zones of an AC building characterized by relevant building regulations. This study could be applied to the energy saving policies of buildings to directly forecast the actual load conditions of buildings, thereby effectively controlling the energy saving and carbon reduction aspects of construction policies.