The invention discloses a power demand predetermining index construction method based on business expansion data. The business expansion data is preferential to power data, a relation between business expansion and electricity consumption is mined, a power demand trend is predetermined, and the method is more direct and accurate than economic prediction of electric power. The service expansion is that a power user, based on a judgment of his own future short-term power demand, brings forward such service requests as new increase, capacity increase, capacity reduction, account cancellation, pausing, pause recovery and the like, and the service requests are accepted and completed by a power enterprise. The method comprises three steps: step one, obtaining source data and cleaning the data; step two, calculating an operation capacity and performing quarterly adjustment on monthly and quarterly data; and step three, constructing a power demand predetermining index. According to the invention, the power demand predetermining index based on the service expansion data is obtained for determining a future power demand.