The image files of regional flooded area obtained by NOAA/AVHRR are transformed into a desk geographical information system(ArcView3.1),so that the covering types and area of flooded surface can be estimated with the aid of the Geography Information System(GIS).The main techniques used are as follows:the method of border test is used to recognize the flooded area in the BMP images;the coordinates of longitude and latitude in marctor projection are transformed into the coordinates of kilometer grid in Gauss-Laguerre projection;the key writing techniques of Shapefile is described in an example of the flood in Liaoning Province in August 4,1995.