Abstract: In wire-line core drilling of horizontal holes, the rotation axis of the drilling tool is not in a straight line with its own gravity direction; with the ground hole pressurized, the drilling trajectory will be deviated due to the soft and hard formation or the occurrence of the rock formation. At present, there is no effective way to achieve directional deviation correction while drilling. This paper studies the pushing, fixing and fishing technologies of small-diameter horizontal wire-line directional instruments while drilling. A set of horizontal rope directional drilling tools and directional technology are developed and applied in directional deviation correction while drilling in horizontal drilling of Duoji tunnel in Sichuan-Tibet Railway. It has successfully restrained the upward drift of the borehole and lowered the inclination by 3°. It will provide support for trajectory control of horizontal wire-line coring directional drilling in geological exploration.