Doppler radar products of damage wind process in Linyi，Shandong on 28 April 20 06 were analyzed. The echo was a typical bow echo, in the front of the bow echo a supercell developed with “VNOTCH”, BWER, then mesocyclone and heavy ra in occurred. After heavy rain, the top of the storm, the height of storm centroi d and maximum reflectivity fell rapidly. The damage wind occurred at this time. Investigated data shows that the path of damage wind go along with the path that the right edge of the mesocyclone passed. It suggests that the horizontal mom entum of the mesocyclone was brought down to the surface by heavy rain. At the right edge of mesocyclone the momentum and RIF have the same direction, the t wo airflows overlay togetherand make the wind increase, so damage wind occurred.