Objective To analyze the epidemiological characteristics of an influenza A outbreak in a school,providing reference for the daily prevention and control of infectious diseases in schools and the management of outbreaks. Methods Case data information was actively searched and collected,throat swab samples of some cases were collected for laboratory testing,data were collated and SPSS 26.0 software was applied for data analysis. Results A total of 54 influenza like cases were found in the school outbreak,with an attack rate of 6.80%.There were 52 student cases,with an attack rate of 7.04%,and 2 teacher cases,with an attack rate of 3.64%.There was no significant difference in the attack rate between teachers and students (χ²=0.474,P=0.491).The attack rate among different grades was not the same,and the difference was statistically significant (χ²=121.431,P<0.001).Among 54 influenza like cases,there were 28 male cases with an attack rate of 7.04% (28/398) and 26 female cases with an attack rate of 6.57% (26/396).There was no statistically significant difference in the attack rate between males and females (χ²=0.069,P=0.793).Among the 54 cases of influenza,32 cases (59.26%) were registered as missing classes due to illness,and 22 cases (40.74%) were screened in the morning and afternoon.A total of 14 throat swab specimens were collected,among which 10 (71.43%) tested positive for H1N1 nucleic acid. Conclusion This is an outbreak caused by the H1N1 influenza virus.The key to the prevention and control of school infectious diseases is to standardize the tracking of school absences due to illness,morning and afternoon examination,as well as early detection,early reporting and early disposal.