In this paper, the authors 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. The authors 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. It shows a medium-and short-term criteria. Distance between earthquake swarm and future earthquake distributed dispersedly.