Abstract: Objective The purpose of this study waS to canvass the rules，characteristics and influential factors of epidemic encephalitis B (abbr．Type B encephalitis) in order tO provide a scientific basis for implemen-tation of preventive and cure countermeasures．Methods Case investigation WaS applied tO all epidemic cases by monitoring the density and species of mosquito medium in homes and corrals，and ELISA WaS used tO determine IgM antibodies of type B encephalitis in serum samples at acute stage．Results There were a total of 40 onsets in this epidemic，with a rate of 2.7/1akh；6 cases of death，with a mortality of 15.0％；the epidemic peak was between late May and early June．Which accounted for 75％ of the total；patients were all under 8 years old，of which those aged between 1 and 6 accounted for 92.5％；all cases were distributed in rural regions and 97.5％ were scattered children resident；85.0％ of caseS had no history of type B encephalitis vacdnation；prima—ry dinie manifestations were hyperpyrexia，spasm，lethargy and positive meningeal irritation sign；monitoring of mosquito medium indicated that the prindpal species of mosquito in local region was composed of Culex tritae—niorhynchus and Armigeres obmrbans，accounting for a ratio higher than 86.3％；serological testing wass used for 39 cases by antilbodyy-capture ELISA, 37 of which were identified aS type B encephalitis IgM antibody positive．Conclusion In the last decade，typeB encephalitis took place and caught on yearly in Guangxi Autonomous Re-gion at different levels of severity and the fulfillment of full-colurse vaccination among sporadically living children in rural regions is pivotal in preventing the outburst and epidemic of type B encephalitis in Gumagxi．