Many problems were encountered in tunnel engineering investigation for the SichuanTibet Railway project, such as large workload, great resistance to drilling tools, large drilling distance, great drilling difficulty and high down hole incident rate. The existing technology cannot meet the requirements of horizontal hole drilling of the tunnel project. Based on full investigation of the present status of horizontal hole drilling technology in petroleum, coal and geological exploration industries, this paper analyzes the movement law of rotation and vibration of the wire line core drilling tool for horizontal hole drilling in tunnel exploration, and the critical load calculation formula is developed for the ultimate bending moment with the drill pipe at both the buckling and the critical bending state. The friction resistance on the drilling tool is studied by numerical simulation.