Abstract: Objective The present study was conducted to find out the situation on the incidence of epidemic encephalitis B, objectively study the epidemic trend and the related factors of the disease further, and analyze the dynamic regulation of the onset in order to provide basis for the decision whether adults should be inoculated the encephalitis B vaccine. Methods The uniformed individual case questionnaires were adopted to investigate the cases with encephalitis B reported in Zibo City from 1995 to 2005. The case database was established by Microsoft Excel, and descriptive epidemiological methods were used to analyze the cases. IgM antibody against encephalitis B in the serum was detected by EIA during the acute period. Results From 1995 to 2005, 338 cases with encephalitis B had been reported, and the average annual incidence was 0.78/Lakh. The cases distributed in 7 counties or regions of Zibo City. 299 cases with encephalitis B were adults at the age of more than 20 years old, who accounted for 88.46% of the whole cases. There were 44 dead cases accounted for 97.78% of all the dead cases. Conclusion Cases with encephalitis B are mainly the middle-aged and old persons in Zibo City. Inoculation with the vaccine of encephalitis B in adults is very necessary to decrease the incidence of encephalitis B, to which should be paid attention by related departments.