Abstract: A bow echo found in a radar observation of a severe storm is described. The characteristics, formation and structure of this echo are discussed, and the relation with the mesoscale system is analysed. It is shown that Fujita model is also suitable to mesoscale system. It is pointed out that cyclonic and anticyclonic motions would appear in the rotating head part and tail part of the bow echo, respectively. The forward movement of the tail is in a way of propagation and closely linked with divergence and convergence of near surface flow.