Abstract: Objective An outbreak of norovirus caused diarrhea occurred in a primary school during 4-7 in June, involving 13 students. The patients were all in class 6 grade Ⅲ. The attack rate was 31.00%.The main symptoms were vomiting(76.92%), diarrhea(46.15%) and fever(7.69%). Norovirus GI was isolated from the patients' stool samples. By retrospective cohort analysis, the possibility of food and drinking water caused outbreak was excluded, and the outbreak was confirmed to be a cluster of norovirus GI infection due to the close contracts among the students.