The invention provides an optimizing method for the running mode of a power distribution network. The method comprises the following steps: S1) acquiring the related parameters for the optimizing of the running mode of a power distribution network; S2) according to the related parameters for the optimizing of the running mode of the power distribution network, constructing a mathematic model for optimizing the running mode of the power distribution network; and S3) seeking the mathematic model for optimizing the running mode of the power distribution network to obtain the optimization result of the running mode of the power distribution network. According to the invention, besides the optimization targets in the prior art such as economy and reliability, another two targets are added: the running risk and grid risk wherein the former reflects the running conditions of the lines and the transformers while the latter reflects the results incurred from a predicted accident. Compared with the traditional optimizing method, the optimizing method of the invention is more comprehensive and the optimization on the running mode is more scientific and reasonable.