Abstract: Objective To examine molecular epidemic characteristics of an adenovirus infection outbreak in a middle school in Liaoning province in 2012.Methods Data of the cases of the infection outbreak were collected.Throat swabs were tested with multiple polymerase chain reaction(PCR)for adenovirus identification and the viruses were isolated simultaneously.L1 of Hexon gene in adenovirus genome was sequenced and blasted.Phylogenetic tree of L1 of Hexon was constructed with neighbor-joining method by using Mega 5.1 software.Results Totally 24 students with fever were found in 3 classes during a month.The incidence of the disease between boys and girls was not different,but the incidences among classes were different.Five throat swabs were positive for adenovirus and 5 isolates were isolated at the same time from the same throat swabs of the patients.The nucleotide identities of the 5 isolates were 100% and basic local alignment search tool(BLAST)analysis showed that 5 isolates were 100%homology with adenovirus 14.The 5 adenovirus were in the same branch with other adenovirus 14 in the phylogenetic tree.Conclusion The pathogen of this outbreak was adenovirus 14 and the virus was not mutated compared with the adenovirus 14 prevalent before in China.