We systematically analyzed 36 earthquake swarms in Jiangsu Province and its adjacent area，summarized the characteristics of earthquake swarms and discussed the relationship between earthquake swarms and strong earthquakes afterwards． We also analyzed the criteria of precursory earthquake swarm． Earthquake swarms in Jiangsu Province concentrated in several places． Most of them were of magnitude ML2. 0 ～ 3. 9． For most earthquake swarms，the number of earthquakes was less than 30． Time duration for about 55% of earthquake swarms was less than 15 days． The biggest magnitude of one earthquake swarm was not proportional to the number of earthquakes and time duration． 75% earthquake swarms were corresponded with one of the forthcoming earthquakes with M ＞ 4. 6，with time interval less than one year． This shows a medium-and shortterm criteria． Distance between earthquake swarm and future earthquake distributed dispersedly． There were no earthquake occurrence in the place of earthquake swarms． There was no good relationship between the magnitude and corresponding rate of future earthquakes and magnitude of earthquake swarms． There was also no good relationship between the amount of earthquakes in earthquake swarm and the corresponding rate． It is better to use U-ρ or all-combinations to determine the type of earthquake swarm．