Objective To analyze the epidemic factors of an outbreak of Norovirus infectious diarrhea in a middle school in Hubei Province, so as to provide a basis for prevention and control measures. Methods The case was investigated by field epidemiology, and the outbreak data and various factors were analyzed by descriptive epidemiology and case control. Results The outbreak involved 91 of suspected cases and 2 cases of latent infection, with an incidence of 33.8%(91/269). Of the four chefs, two were silent infection. The first case was from class 8-2 at 7∶30 on February 15th. 69.2% (63/91) of the cases occurred from 8∶00 to 24∶00 on February 15th, with median of 16∶00. The result of the case-control study suggested an increased risk of eating breakfast on February 14th [odds ratio (OR)=9.93,5% confidence interval(95%CI):1.17-84.04]. Conclusion This event was an outbreak of infectious diarrhea caused by Norovirus. In the peak season of Norovirus infection, the monitoring of infectious diarrhea in collective units and schools should be strengthened, and health education should be actively carried out, so as to effectively prevent the outbreak of infectious diarrhea caused by Norovirus.