Abstract: A pressing method of radar data is introduced in this paper. As the value changed sharply near the borders of echo intensity layers, the isopleth is drawn out by differential processing. Actual process is made for several times. Each time the layer thresholds are altered to keep a certain interval and the quality of the isopleths is highly improved. The points on the isopleth are lined rapidly by comparing the sequence of distance among points and the intersected isopleth is corrected by tracing against a change coordinate. The echo border is filtered by diaphragm method. After filtered the distorted borders are mended and echo structure is more obvious. Optional layer can be filtered and others are kept unchanged. By the method mentioned above only 7 percent original data is used to store or display an echo chart. The pressing rate achieved 93 percent