Abstract: Based on the site practice of Cezi Waterway Horizontal Directional Drilling (HDD) operation, the paper describes key issues which should be taken account of in large diameter, long distance and complicated geologic conditions, emphasizes the principle in drilling-route selection and drilling-curve design. Meanwhile, the paper makes technology analysis to such field practices used under this condition as pilot-hole drilling technique, reaming technique, the application of special boring tools, and direction control techniques, and the method of boring-hole assembly in case of emergency condition is solved effectively.