To investigate an outbreak of acute upper respiratory tract infection in a kindergarten, and help to better manage the future outbreaks.Methods Epidemiology data, clinical information and laboratory test results of all the cases were analyzed with descriptive epidemic method and statistics method. Results The attack rate of adults were 56.92% (37/65). No children got sick. The main symptoms were pharyngeal hyperemia, pharynx aches, fatigue, fever and acute tonsillitis, etc. Drinking yoghourt was the main risk factor (OR=3.34,95%CI:1.08-10.32). The Streptococcus dysgalactiae subspecies equisimilis (SDSE) was detected in the cases′ pharynx swab samples and the detection rate was 76.92% (10/13). Conclusion SDSE was the pathogen of this food poisoning. The outbreak of acute upper respiratory tract infection with SDSE-contaminated food seldom occurs in China. Isolation and identification of SDSE is the key to its rapid diagnosis.