The safe operation of power grid is affected seriously by transmission line galloping. Based on the influencing factors of transmission line galloping,the fuzzy mathematics theory is applied in the early warning of transmission line galloping. An early warning model of transmission line galloping based on the improved fuzzy hierarchical comprehensive evaluation method is proposed. Firstly,five major impact indicators including wind speed,rainfall,relative humidity,air temperature and wire tension are screened out to construct an early warning evaluation factor set. Four evaluation target sets including level IV,level III,level II and level I are constructed. Then the monitoring data is substituted into the model calculation. The early warning information is issued according to the fuzzy comprehensive evaluation results,which provides guidance for staff to perceive line risk events and prepare for disaster prevention. Finally,the early warning auxiliary decision-making system of the transmission line galloping based on ArcGIS Engine is developed to achieve the visualization of early warning information,and the actual line data is selected to verify the effectiveness of the proposed method. The results show that the proposed early warning method provides decision support for the safe operation of transmission lines.