Based on 4 year observation data (2005—2008) acquired by Doppler weather radar located at Yancheng, the relationship between mesocyclones and the severe convective weather is analyzed. The results show: (a) There is a high probability of large hail occurring on the right flank of the storms with high top and bottom of mesocyclones; (b) A storm with lower bottom and smaller diameter of mesocyclone is favorable for tornado; (c) Rear inflow jet can intensify the wind shear of mesocyclone, make the mesocyclone descending, thus produce downdraft and strong wind; (d) The mesocyclones located on the front flank of storm with lower bottom and weaker wind shear usually cause heavy rain. Convective storm containing mesocyclone usually occurs in the environment with high CAPE and strong vertical wind shear.