Abstract: There was a serious flood along Yangtze River in early summer 1998. The Ministry of Health sent an investigating group on communicable diseases control after severe flood. Shangrao county Jiangxi province was chosen to investigate as where were more cases with leptopirosis were reported. The outbreak began on July 29. The incidence rate was up to top within 6-7 days and the outbreak was controlled within 2-3 weeks. Up to Sept. 2, 456 cases with leptosprosis were occurred (male 355, female 101). The incidence rate was 66.09/106.Four patients were died (male3,female1).The mortality rate was 0.88%.34 patient's serum samples were collected for laboratory examination to test the accuracy of chinical diagnosis.The positive rate by the microscopic agglutinatin test (MAT) was 76.47%(26/34) and by dot-ELISA was 82.35%(26/34).