Objective To explore the causes and characteristics of an acute gastroenteritis outbreak with the main symptoms of vomiting, abdominal pain, diarrhea, and provide scientific basis for formulating prevention and control measures. Methods Defining the cases and carrying out the epidemiological investigation, collecting the samples of body excretions from cases and dubious water to detect the pathogenic microorganism. Results The cumulative incidence number of this outbreak was 99 cases. The incidence curve of this outbreak showed a single peak tail band and focus on March 1st to second, lasting for 11 days, showing point source exposure. After March 3, there were still a small number of cases. There was no exclusion of the emergence of the two or three generation because of cases of contact.The attack rate of male was 0.39%, and female was 0.32%. There was significant difference in incidence among villages(χ²=72.469,P<0.01), while there was significant difference in incidence among different age groups nor between genders. The closer the pipe network near to the water plant, the higher the attack rate was. The incidence of people drinking running water in the town was 0.81%, drinking other water was 0.03%, and the difference was significant (RR=26.238,χ²=114.692,P<0.01). Among 28 cases of stool, anal swab and vomiting specimens, virus nucleic acid were detected from 27 cases specimens, and the positive rate was 96.43%. Gene sequence analysis showed it was norovirus G typeII.17. Conclusion This epidemic acute gastroenteritis outbreak was due to water pollution of norovirus G type II.17. Improper location of the water source plant in rural areas and lack of protection,a heavy rain and lack of supervision were some risk factors of the event.