The invention provides a power distribution network fault studying and judging method and system. By analyzing the conditions of voltage and current of electric energy meters and transformers of users in a detailing mode, the type of a fault is determined, the affecting range of the fault is determined, the workload for emergent repairing workers after the emergent repairing workers arrive at the site is lightened, the emergent repairing progress is accelerated, and the power fault is removed in time. Meanwhile, before study and judgment begin, whether the fault is caused by arrearage of users is judged, if yes, the judgment is that the fault is caused by arrearage of users, and the study and judgment process is stopped. Therefore, the workload of the study and judgment system is lightened, and the study and judgment time is shortened.