Aiming at urban accidents that affect the development of urban economy and social stability, this paper discussed the dynamic simulation models and techniques of typical urban fatal accidents, and developed the assistant decision support system for urban emergency response. The function of this system included： Dynamic simulation of the typical accident of different functional district of city; Decision for the response to grave accident of different functional district of city; Emergency preparedness plan database for different functional district in the city and different type of accidents; Decision for response to grave accident of city and decision for commanding and dispatching. This system used advanced information management and engineering, could find the hidden accident, control the accident and rescue in time, thus reduced the property loss and casualty to minimum extent.