How to make full use of existing information to improve the accuracy of fault diagnosis in distribution networks, and provide accurate research and judgement for emergency repair of distribution networks, is an urgent problem to be solved. To address the problem of the single source of fault diagnosis information in existing distribution networks, a fault diagnosis model of distribution network is proposed which integrates the medium and low voltage information of the distribution networks and the outgoing current information of the substation. The model first applies the existing overcurrent diagnosis method to the problem of large-scale distribution network, and adopts hierarchical reduction of the size of the distribution networks to improve the location speed of fault section. Then, in view of the accuracy of overcurrent alarm information, an auxiliary fault judgment method for distribution networks based on switch relay protection sequence of events (SOE) data and substation outgoing load sag data is proposed. Finally, the steps for fault diagnosis in distribution networks of multi-directional information and data fusion in practical engineering are summarized, which provides reference for fault diagnosis of dispatchers. Engineering practice proves that the method proposed in this paper can effectively diagnose faults and is very adaptable to large-scale distribution networks. The auxiliary diagnosis model combining switch operation SOE and telemetering voltage information can compensate for the accuracy requirements of the overcurrent diagnosis model for remote communication information, which is complementary to each other and has a good engineering value.