The invention discloses a business-index-based method and system for predicting electricity consumption. The method comprises: obtaining power indexes of a to-be-predicted electricity consumption industry within a time period; carrying out pretreatment on the power indexes; screening leading indicators out from the power indexes by using current industrial electricity consumption as a benchmark; according to goodness of fit, time difference correlation coefficients, and autocorrelation coefficients of all indexes in the leading indicators, determining weights of the indexes; on the basis of the weights of the indexes, determining a leading synthesis business index; according to the leading synthesis business index and the time difference correlation coefficient of the current industrial electricity consumption, determining a leading cardinal number; on the basis of the leading cardinal number, carrying out regression fitting on the leading synthesis business index of the to-be-predicted electricity consumption industry and the current industrial electricity consumption of the to-be-predicted electricity consumption industry; and on the basis of a regression fitting result, predicting industrial electricity consumption of the to-be-predicted electricity consumption industry. Therefore, the industrial electricity consumption can be predicted accurately and the decision-making basis can be provided for development of the future power industry.