Abstract: With the rapid development of the Web and GIS technologies,it has been feasible and necessary to design a good sized flood control and command information service system.Nearly associated with the practice of the Heilongjiang Province flood control and command information service subsystem,the Web GIS's solution based on the ArcIMS is researched in this paper,and the several key techniques of applying the ArclMS are studied.The techniques are as follows:(1) Taking the obverse and the reversal information queries as examples,the data flow of the information query is researched and designed; (2) For the convenience of managing and using the spatial data,the method for dividing and organizing the map layers is studied;(3) For the economical and practical purpose of system,the switch between the different scale maps without sight equation is researched;and (4) According to the user's demand to display the map,how to write the map configuration file is discussed.The effect of these key techniques,which are applied to the practical design and development,is also illustrated.