Objective To understand the infection status, epidemiological characteristics and genetic evolution of adenovirus in children with diarrhea in Tianjin. Methods A total of 1609 fecal specimens were collected from hospitalized children with diarrhea from July 2017 to July 2018 in Tianjin Children's Hospital. Viral nucleic acid was extracted and amplified by the hexon gene fragment. Positive specimens were used for nucleic acid sequence determination and sequence alignment and phylogenetic tree analysis with known sequences in GenBank. Rotavirus in the stool specimens was detected by gold standard method, and campylobacter was detected by latex agglutination method. Bocavirus, Norovirus and Clostridium difficile were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Results A total of 69 specimens with adenoviruses were detected in 1609 cases, with a positive rate of 4.3％, in which 82.6％adenovirus-positive children were between 7 and 48 months old. The positive rate of adenovirus peaked in the summer and autumn, and the differences of this value among seasons were statistical significance (χ2=11.467,P=0.009). In these cases, the mixed infection rate of adenovirus was 26.1％(18/69), in which 7 cases were mixed with Norovirus, 7 cases were mixed with rotavirus and 4 cases were mixed with Clostridium difficile. A total of 39 adenovirus-positive PCR products were randomly selected for gene sequence detection, and 7 adenovirus genotypes were detected. Results showed that these viruses were mainly the type 41 enteric adenovirus (46.1％, 18/39), followed by type 31, type 3 and type 7 non-intestinal adenovirus, while types 1, 5 and 6 were relatively rare. Conclusions There are diverse types of adenovirus in children with diarrhea in Tianjin. The adenovirus-infected diarrhea mostly happen in summer and autumn, and is common in children.