Abstract: Polar coordinate divergence method is one retrieving divergence from single Doppler radar velocity data in the polar coordinate. Using this method, we can retrieve the components of radial divergence and radial movement without any assumption. Only when calculating the component of tangential divergence, an assumption of a constant wind field within a small sector region is required to retrieve the tangential velocity. The error analysis shows that the calculating error is about one order of magnitude smaller than the retrieved divergence. A retrieving test of divergence is made in a cold front process. The result shows that the method cold be applied in the analysis of mesoscale system.