Objective To determine the epidemiological characteristic,clinical feature,laboratory examination of encephalitis B in Wuhua county Methods The epidemiological data and clinical feature of encephalitis B cases were analyzed. Results The patients age range was 8 months to 11 years old, and the epidemic period was from May 27 to June 30. The cases of Encephalitis B distributed over 22 towns with no family gathering. 99.5% of cases had no history of vaccination and all of the cases had fever, twitch and coma. There were 86.4% of patients with stiff neek, 63.6% with klinefelter's syndrome, and 68.2% with Brudzinski' syndrem. Leucocyte total average was 16.8×10 9/L, and neuter granule cell average was 8.5×10 9/L. The IgM antibody positive rate of Encephalitis B was 46.2% in the early serum examination. After comprehensive treatment, 2 patients died with the death rate 4.5%. Conclusion The prevalence of Encephalitis B presented a very strict season and age characteristics. The poor living condition, massive media insects, the shortage in epidemic prevention in rough area, and low vaccination rate were main factors. It was improtant to emphasis the epidemiological analysis, to develop the diagnosis and inspect ability, and to control the disease prevalence of as early as possible.