Abstract: Objective To understand serum antibody level to Japanese encephalitis (JE) among suspected cases, provide scientific evidence for the prevention and control of JE. Methods The detection of IgM antibody in serum samples at acute phase and IgG antibody in double serum samples collected from suspected cases in Qiandongnan prefecture from 2007 to 2009 were conducted by ELISA, and epidemiological analysis of confirmed cases were made. Results A total of 174 serum samples were detected,88 cases were positive for JE antibodies, the positive rate was 50.57％. Up to 73.86％ of the cases were distributed in Congjiang, Kaili, Huangping, Shibing, and Rongjiang counties. Most cases occurred during June-August. The JE incidence and positive rate in males were higher than in females(2＝9.83,P0.01)(2＝4.80,P0.05), and 73.86％ of the cases were the children under 15 years old. Of 98 serum samples collected from 2008 to 2009, the positive rate was highest among the samples collected within 8-14 days after onset(75.00％), followed by the samples collected within 4-7 days (67.74%). Conclusion It is necessary to strengthen the prevention and control of JE in Qiandongnan by improving immunization quality and conducting IgM and IgG detection to identify JE cases and epidemic.