Abstract: Erlangshan is the first mountain block alony the Chengdu-Kang Zhang highway. The exploration and field geological experiments for the scheme of the tunnel line choice was decided in 1944 after inspecting and demonstrating many tunnel scheme by relating transportation departments responsible for the work. By hydrogeological exploration, flow logging and pulse experiments, the hydrogeological conditions of tunnel spots have been ascertained, and the hydrogeological paramenters of each aquifer have been obtained, the total tunnel discharge and the excessive discharge sections have been predicted.