After the paper describes briefly the principle and processing technique for measuring the wind field in echo area by use of moment invariant method, the wind vectors of every module in actual PPI echo data observed by digitized conventional weather radar are estimated. In order to value quantitatively the accuracy, the estimated vectors are projected onto radar azimuth to obtain radial speed estimations. And the estimations are then compared with the radial speed field observed simultaneously by single Doppler radar. The results of comparison for four cases in two precipitation processes show that average accuracy is near 80%, and above 90% if the edge effect is eliminited.