Emergency monitoring is a very important step in response to dealing with sudden air pollution accidents; however, the traditional monitoring methods sometimes appear passive effects in practice, owing to the lack of techniques. In this paper, we presented and discussed the overall requirements analysis, the system architecture, four function modules and three key technologies of the emergency monitoring system to sudden air pollution accidents. Through analyzing the working process of air pollution emergency monitoring, we proposed that the design and development of the system should base on the storage and management of a variety of emergency monitoring data, and accord with the working process of emergency monitoring. The system uses Client/Server architecture, and is deployed in the Local Area Network to ensure a highly safe reliable and real-time environment. In this paper, we discussed the four function modules in detail and analysis the three key technologies that contain spatial information processing. The four function modules are basic information management, emergency monitoring response, spot emergency monitoring and recovering monitoring. And the key technologies are the location and query of varieties of spatial objects, the definition of air pollution accident danger zone through integrating Gaussian pollution dispersion model, and the expression and analysis of monitoring data by comprehensive use of statistical charts and contours. The result shows that comparing with traditional methods, this emergency monitoring system helps to respond sudden air pollution accidents more rapidly for the emergency monitoring staff.