The invention discloses a power distribution network input and output evaluation system index simplification method comprising the following steps that 1) a power distribution network input and outputevaluation index system is established; 2) the existing indexes are classified according to the characteristics of the power distribution network and the whole index system is divided into multiple levels; 3) the weight of each index is calculated, the important indexes are determined according to the size of the weight and the secondary indexes are deleted; 4) the degree of correlation between all the indexes is analyzed according to the index system obtained by simplification of the step (3) and the indexes are screened; and 5) the weight is assigned to each index of the index system beforeand after simplification, the comprehensive evaluation score of each city is obtained based on the actual data and the rationality and the effectiveness of the index system after simplification are comparatively verified. According to the method, index simplification and the correlation and the importance between the indexes are considered in the establishment process of the index system so thatthe redundancy between the indexes can be avoided, the evaluation efficiency can be enhanced, the information integrity after index simplification can be guaranteed and the rationality and the effectiveness are high.