Using data of power transmission line galloping (which happened 3 times from 2009 to 2010) in Henan Province and observations from representative stations, characteristics of line galloping are analyzed and meteorological indices for transmission line galloping are obtained. It shows that transmission line galloping will happen when the following conditions are satisfied: (1) A cold layer exists near 850 hPa where the temperature is less than -4℃ and a layer warmer than 0℃ exists below the cold layer. Alternatively, a layer warmer than 0℃ near 700-850 hPa and a cold layer exists below the warm layer; (2) the difference between temperature and dew point temperature below 700 hPa is less than 2℃; (3) the surface temperature ranges between -4℃ and 1℃, the wind speed is greater than 3 m·s-1 and the relative humidity is greater than 70%. Finally, the meteorological indices are used to draw the galloping distribution map for the galloping process monitored in 22-24 November 2015 in Henan Province. It is found the galloping grids predicted with the indices can cover the galloping monitored towerpoles. Thus, the indices are reasonable and applicable.