The epidemiologic field investigation was conducted to analyze the epidemiological characteristics and influencing factors of an epidemic of hepatitis A that was locally prevalent in Wantian township of Ruijin city. The incidence rate of this 89-day epidemic was 274.36/lakh, with 35 hepatitis A cases reported, showing an increase of 2864.94% compared with the average incidence of the past 8 years. The 5-to-10-year-old primary students and pre-school children were mostly affected in the epidemic. In close contact with the patients, 54 people were found HAV-IgM positive, the positive rate being 28.57%. It was believed that the epidemic was transmitted through casual contact. Hepatitis A and asymptomatic infected patients were the key sources of infection. The emergent inoculation of gamma globulin was critical in the control of hepatitis A.