To analyze large-scale public buildings’ energy-saving potential is one of the methods to realize scientific energy control management and service. This method aims at a typical public building’s powerconsumed system. Through analyzing and comparing the consumption data, it succeeds in analyzing the use efficiency of building power, consumption level and economic effects of the energy utilization. More over, this method has a quantity analysis on the power-consumed unit’s building usage, so that it is able to find the unit’s energy-saving potential. Its bases of all analyses are building energy balance and analyzing theory of energy cost, analyzing theory of engineering economy and environment and rational distribution theory of energy utilization system.