Abstract:The basal data of volume scanning of Doppler radar is extrapola ted．Based on the ripe COTREC (Continuity of Tracking Radar Echo b y Correlation vectors) and centroid tracking technique，the “sub pixel" veloci ty is computed by Fourier phase analysis technique, so the echo data and its image are obtained through extrapolation．Furthermore，the distribution of precipitat ion intensity is worked out based on the Z R formula．The extrapolated resu lts with and without use of sub pixel velocity are compared with actual intensi ty data of volume scanning，the distribution of precipitation and one hour preci pitation (OHP) product of PUP in WSR 88D are compared with the data of automati c precipitation station records． The analysis results indicated that the accura cy of using sub pixel velocity in extrapolation is higher than t hat of non use，and the re liability of one hour precipitation through extrapolation is greater than the OH P of PUP．The extrapolation technique is tested in different kinds of weather pr ocess. The findings show that this technique is applicable，can improve the tech nique of TREC, and has some referenced value in nowcasting．