Abstract: Large-scale public places and essential public facilities are areas with highly concentrated population. In order to safely evacuate peoples in emergency situations, it is necessary to make emergency schemes for such areas in advance. However, making emergency scheme for such places and facilities is very difficult due to their high complexity in architecture and high density population. Virtual drilling of crowd evacuation under emergency scheme is a new technology to hit these problems. By using virtual reality technique, 3D virtual crowds and public facilities are generated in computer generated space and the process of evacuation is simulated under the given assumption of security crises and emergency scheme. The authors could also 3D-display the scenes of evacuation and statistically analyze the results, which are very useful for verifying the rationality and validity of the given emergency scheme. This paper introduces a system named Guarder, which is a virtual drilling system for crowd evacuation under emergency scheme. The core idea and technical framework of the system are introduced in details. Key technologies including semantic description for complex environment, crowd simulation and so on are deeply introduced. After that, several experiments and applications of the system Guarder are demonstrated to show the success of the technique design in Guarder. Moreover, some hot research topics are presented.