Objective To investigate the etiology and epidemic characteristics of infectious diarrhea in children in Suzhou, and to provide a basis for accurate prevention and control. Methods Active surveillance of infectious diarrhea pathogens was carried out in a national sentinel surveillance hospital in Suzhou from 2018 to 2020. Epidemiological investigation was completed and stool samples were collected. All samples were detected and classified for 5 viruses and 6 types of bacteria. Results A total of 999 cases of infectious diarrhea were included, the detection rate of pathogen was 36.34%, virus was 31.41%, bacteria was 6.31%, and multi-pathogen mixed infection was 4.8%. The top three pathogens were rotavirus (17.92%), norovirus (12.51%) and Salmonella (3.4%). Both rotavirus diarrhea and norovirus diarrhea occurred most frequently in children aged 7-24 months, with peak incidence in winter and early spring. There was no obvious seasonal and age distribution of bacterial diarrhea. The multi-pathogen mixed infection was mainly virus-virus. G9[P]8 was the dominant genotype of rotavirus, while type 2 was the dominant type of norovirus in the cases of infectious diarrhea. Conclusion Infectious diarrhea in children under 5 years old in Suzhou area from 2018 to 2020 is mainly caused by viruses, among which rotavirus and norovirus are the dominant pathogens. Viral diarrhea has obvious population distribution and seasonal characteristics. The dominant pathogens of bacterial diarrhea are Salmonella and diarrheagenic Escherichia coli.