A Unity 3D based three-dimensional virtual crowd scene generating method includes 1, establishing a database; 2, establishing a static virtual environment; 3, creating an event; 4; creating figure models; 5, creating a story control object and constructing an event tree, an event trigger generation sub object, an event selection sub object, an event confliction detection sub object and a crowd dynamic generation sub object in the story control object; 6, calling the story control object by a game engine to generate a three-dimensional virtual dangerous environment; 7, implementing the construction of the three-dimensional virtual dangerous environment. According to the invention, uniform design of crowd, environment and event is preformed, function completeness is achieved. By employing assemblies and plug-ins provided by the Unity 3D game engine, development operation is simplified. The invention synthesizes basic design elements required for virtual crowd scene development, improves efficiency of virtual crowd dangerous scene generation and similar game environment development and has advantages of function completeness and high development efficiency.