Abstract: In Qinling mountain where Xi'an-Nan jing railway going through, topograghy and geological condition is complex and the earth crust has been under going endless geological term. The complex geological enviroment has been formed, affected by strongly structural force and outer force. In which,as selecting railway, various engineering geological problem will be met. The main problems and it's treating have been analysed so as to give a reference about selecting railway line and treating in mountain area in future.