The invention provides a comprehensive assessment method of a power distribution network operation mode. The method comprises the following steps: selecting a main index and a plurality of sub indexes from a plurality of preset assessment indicator systems, and building an assessment model comprising an objective function and constraint conditions; performing transformation on the assessment model based on the lagrange function, and calculating lagrange multipliers corresponding to the various sub indexes; and building a result assessment function based on the assessment model after the transformation, introducing the lagrange multipliers corresponding to the various sub indexes as weighted values corresponding to the various sub indexes to the result assessment function, obtaining a plurality of result assessment values, and determining an operation mode, which corresponds to the minimum in the result assessment values, for being the best. The embodiment of the invention is implemented, indexes related to operation of a power distribution network are fully considered, the comprehensive assessment function is built by utilizing the lagrange function in nonlinear programming, subjective factors incorporated in the assessment process are reduced to the maximum extend, an assessment result is more reasonable, and expandability is possessed.