The invention discloses a distribution network planning method based on a credibility theory, which comprises the steps of S1, building a distribution network fuzzy planning model based on the credibility theory; S2, building an equivalent model with a given reliability index; and S3, solving the model by adopting fuzzy power flow calculation and a genetic algorithm. According to the invention, the distribution network planning model based on the credibility theory is built on the basis of a fuzzy mathematic theory, the fuzzy uncertainty of load is considered, the minimization of the fixed investment and the fuzzy expected loss cost of the distribution network within the planning period is taken as an objective function, the reliability index is introduced, and the branch power and node voltage constraints are processed by adopting fuzzy change constraints; and secondly, the distribution network planning model under the credibility index is equivalent to a distribution network planningmodel under interval load by adopting a credibility index equivalence theorem, and a cut set corresponding to the fuzzy load distribution is enabled to be expressed by an intuitive interval. In addition, the solving method lowers the model solving difficulty and reduces the model solving time.