Abstract: Objective: In order to solve the multiple relay protection problems in multi\|power supply systems, it is necessary to analyze and study the node interlocking protection methods applicable to various power supply modes. Method: Problems existing in the relay protection of urban rail transit power supply system are elaborated, and the node interlocking protection method is proposed. The adjacent protection is defined by the node, and the positive direction of various protections is specified. The current forward and reverse directions are determined through positive and reverse direction judgement. The signaling criteria and action criteria for reverse blocking protection, permissive protection, and reverse failure protection are mainly studied. Result &Conclusion: Combining application examples, the effectiveness of permissive protection and reverse blocking protection based on this method is proven in overcoming the possible refusal tripping problem of traditional non directional blocking protection in multi\|power systems, and the action time delay of permissive protection can be shorter than that of traditional non directional blocking protection, even if the fiber optic differential protections between lines is not working or configured, This method can still provide complete protection against faults in various power supply modes.