The groud flashover density varies greatly in different locations of mountainous terrain.In order to study the influence of mountain terrain on ground flashover density

this paper firstly analyzed the difference of ground flashover density in different parts of mountain by using Google Earth and ArcGIS software based on the data of lightning location system

and then analyzed the calculation results of lightning shielding failure trip rate of a 500 kV transmission line.It is found that the density of ground flash is obviously larger than the actual situation when the screening range of improved grid method is less than 400 m

and the difference of terrain is offset when the screening range of improved grid method is larger than 1 600 m and meanuhile

the groud flashover density of meuntain top

hillside and flat land tends to loe the same. The lightning density of mountainous terrain varies with the altitude of the mountain

showing the rule of peak-to-ground lightning density > hillside > valley as a whole

and the shape of mountain body will obviously affect the distribution difference of the lightning density of mountainous terrain.The calculated results of shielding trip rate of a certain line are in good agreement with the actual lightning fault section of the line

and this study can provide some reference for differential lightning protection.