The invention discloses a method for diagnosing multiple faults of a power distribution network under imperfect fault information. The method comprises the steps as follows: firstly, obtaining a diagnosis decision table by existing fault information of a power distribution network; then extracting effective information from massive alarm information by complete process classification, and correcting error information in uploaded fault information; finally, writing diagnosis rules into a matrix form, quantifying the probability that a sample to be diagnosed conforms to the diagnosis rules, andobtaining a diagnosis result with the maximum probability. The method can quickly and effectively realize fault diagnosis, and reliability, safety and flexibility of system operation are greatly increased.