The invention belongs to the technical field of electric information, and particularly relates to an efficient fault diagnosis method for an electric power information system. The method comprises thesteps of selecting parameter indexes representing the running state of the electric power information system, constructing a parameter index set, and performing discretization processing on the parameter indexes; constructing an information system fault diagnosis knowledge representation system, and building a decision table; building a fault diagnosis level analysis model of the electric power information system, and determining a parameter index weight in a parameter index set; according to the index weight, sequentially determining a condition attribute set subset, and calculating mutual information of the decision attribute set and the subset of the condition attribute set, and obtaining the minimum index reduction set; according to the index weight and the minimum index reduction set, calculating a final result, and making diagnosis. By building an analytic hierarchy model, the index weight is determined, index reduction calculation is performed according to the weight ranking and mutual information calculation, the reduction efficiency is improved, meanwhile, the reduction set optimization is ensured, and the decision accuracy is improved.