Abstract: This paper discusses in detail the analysis of the inconsistent protection behavior of protection devices on both sides of the line fault. When the line fault occurs, one side of the protection device acts while the other side of the protection device only starts protection. This article from the run situation, the fault description, protection action report, wave record analysis, logic analysis, combined with field patrol inspection, found on both sides of the protection actions inconsistent reason, to provide reference and guidance for similar power supply enterprises processing, and put forward the feasibility of protection device defects prevention measures, to ensure safe and reliable operation of power grid.