Aiming at 3D modeling and analyzing problems of hydraulic and hydroelectric en-gineering geology,a complete scheme of solution is presented. The first basis was NURBS-TIN-BRep hybrid data structure. Then,according to the classified thought of the object-oriented technique,the different 3D models of geological and engi-neering objects were realized based on the data structure,including terrain class,strata class,fault class,and limit class;and the modeling mechanism was alterna-tive. Finally,the 3D integrated model was established by Boolean operations be-tween 3D geological objects and engineering objects. On the basis of the 3D model,a series of applied analysis techniques of hydraulic and hydroelectric engineering geology were illustrated. They include the visual modeling of rock-mass quality classification,the arbitrary slicing analysis of the 3D model,the geological analysis of the dam,and underground engineering. They provide powerful theoretical prin-ciples and technical measures for analyzing the geological problems encountered in hydraulic and hydroelectric engineering under complex geological conditions. Aiming at 3D modeling and analyzing problems of hydraulic and hydroelectric en-gineering geology, a complete scheme of solution is presented. The first basis was NURBS-TIN-BRep hybrid data structure. Then, according to the classified thought of the object-oriented technique , the different 3D models of sedimentary and engi- neering objects were realized based on the data structure, including terrain class, strata class, fault class, and limit class; and the modeling mechanism was alterna-tive. Finally, the 3D integrated model was established by Boolean operations be-tween 3D geological objects and engineering objects. On the basis of the 3D model, a series of applied analysis techniques of hydraulic and hydroelectric engineering geology were illustrated. They include the visual modeling of rock-mass quality classification, the arbitrary slicing analysis of the 3D model, the geological analysis of the dam, and underground engineering. They provide powerful theoretical principles and technical measures for analyzing the geological problems encountered in hydraulic and hydroelectric engineering under complex geological conditions.