Using the data of Nanjing Doppler weather radar (WSR98D), the tornado occurrin g in Tianchang of Anhui Province and Gaoyou of Jiangsu Province on July 3, 2007 was analyzed. The characteristics such as mesocyclone (M) and tornadic vortex s ignature (TVS) were found.The tornado occurred in the strong development supercell located on the north of line echo wave pattern (LEWP), the strong shear of wind direction existed in the front of echo line, and it makes the mesocyclone continuously generated along the echo line. In the cell tornado, mesocyclone (M) products can be worked out 30 min before tornado occurrence, the M lasts for 7 volume scan time lengths (42 minutes), thus TVS products can be worked out at the 5th volume scan of M product appearance, it lasts 3 volume scans, and the combined shear products have also given out notable prompting. According to the field survey, the tornado occurred at the time that the 2nd TVS occurred, it is located on the south side of the TVS, and consistent with the southern fringe of mesocyclone. Although the TVS products may be false at time, but with the checking of reflectivity, the base radial velocity, mesocyclone, combined shear products etc., it is useful for making tornado warning.