By means of a recursive algorithm,the tracking and extracting of the boundary data from the digital image of a map is realized,and then after converted into the corresponding longitude and latitude coordinates,these data can be applied to the meteorological plotting software GrADS,Vis5D,Surfer and MICAPS to plot the background map.With the method,the extracting of the needed messages from the digital image can be realized directly for the difficult-to-acquire longitude and latitude coordinates of boundary points of the map(such as the district boundary lines of a city),so to meet the needs of the intensive meteorological monitoring network and the visualization of high spatial resolution meteorological elements.Solved the problem about the lack of the longitude and latitude coordinates of boundary points of a map,the method can be used in meteorological plotting and to various operation systems.An application example is given.