In 2006, there were 767 reported malaria cases in Jiangsu Province with an incidence of 1.07 per thousand and increased by 16.57% in comparison to the previous year. Positive rate of blood examination in local febrile patients was 0.08% (293/361 896) but 1.23% (251/204 40) in mobile population (P<0.01). Cases with relapses occupied 9.00% of the total. The density of Anopheles sinensis was 0.61 per net and increased by 110% more than the year 2005 (0.29/net). It is indicated that the increase of A. sinensis density has been the main factor for malaria recurrence in the area north of Huaihe River in the Province.