It is difficult to achieve a clear understanding during the survey period before deep buried long tunnels construction， which may affect the construction of the project to some extent. The application of directional drilling technology for the geological forecasts before the construction of deep buried long tunnels is propsed， in which the good guiding function and rapid long distance drilling characteristics are utilized to achieve advanced detection of major risks ahead of tunnel excavation， and it can compensate for the shortcomings of conventional long-distance advanced detections. In this paper， different types of drills are used for geological forecast of 7# tunnel in the water diversion project from Yangtze River to Hanjiang River based on different geological conditions and prediction priorities， moreover， the advanced forecast results and the geological conditions revealed by excavation are compared and analyzed. It is thought that the directional drilling application is aiming to detect major disaster bodies in front of the tunnel excavation face in advance， and the goals can be generally achieved combining the drilling characteristics and physical measures. Furthermore， the timeliness of forecast can be improved while drilling without coring. Based on the current technological level， the efficiency of directional drilling is higher than tunnel excavation of blasting and TBM method， which is feasible in the advanced detection of tunnels constructed by blasting or TBM method.