The overall structure and features of a 3-D GIS-based monitoring and warning system for geological hazard are expounded. Key technologies including information gathering network and communication, temporal GIS, geo-hazard monitoring and warning based on multiple models are analyzed and introduced. The system with multiple layers adopts highly scalable structure and flexible deployment. GIS, virtual simulation, and WEB asynchronous service based on multi-user concurrent are also employed. Through the system, functions of information gathering, communication, management, analysis, decision-making, and warning are integrated. The system is applied to Danjiangkou reservoir as a trial. Finally, the research provides reference for the scientific management of geological hazards and emergency response.