Based on the scatter model（Sato）,using earthquake wave form data with ML≥ 2.0 from 2000 to 2008 recorded by Sheyang and Hai＇an seismic stations in the coastal areas of central Jiangsu province,the Qc values of coda with different lapse time in this region is calculated.The result indicates that this region has low Qc value,and the Qc values increase with lapse time increasing.Before Dongtai ML4.1 earthquake swarm in November,2006 and Xiangshui ML4.0 earthquake on May 6,2007,the Qc values of coda increased apparently.