The Doppler Radar Products during a tornado occurred in Sixian, Anhui Province on 29 Jun 2006 are analyzed. Before the tornado, there were three NESW oriented bowshaped echoes, and the tornado was on the furthest southwest edge of the bowshaped echo. A shortrange heavy rain occurred before the tornado appearing with a rainfall amount of 60 mm in 2 hours. The strong shear of wind direction existed in the front of the bowshaped echo, which resulted in a series of mesocyclones along the front edge of the echo. The southwest bowshaped echo joined the echo in the front of it, 30 min before tornado occurred, and then a large mesocyclone with a diameter of 25.8 km formed. According to the survey, there was a severe wind zone in upstream of the tornado, which was in agreement with the moving path of the south edges of the maximum zones in the mesocyclones. It suggests that along the south edges of the maximum wind zones in the mesocyclones, the mesocyclones and the straight wind behind the bowshaped echoes have the same direction, and the two airflows overlaid together, leading to the occurrence of the severe winds. About 1 hour 40 min before tornado occurred, the radar caught up the mesocyclones, and 12 min before, detected TVS (Tornadic Vortex Signature) products, which are undoubtedly useful for making tornado warning.