Yesanguan tunnel is a key project of the whole Yiwan railway. This paper is based on field investigation and test analysis, firstly researches karst distributing rule of this zone, and studies grade separation of karst water bursting hazard of this tunnel construction through analyzing information. Then analytical methods are discussed. Finally the risky zone and risky grade of karst water bursting hazard of the construction are confirmd through analyzing specific geological and hydrogeological conditions of Yesanguan tunnel. All this result provides the basis for the definition of key prevention sectors of tunnel construction.