In this study, 2 types of drinking water were provided to broiler chicks to evaluate the relationship between the bacterial load of drinking water and cecal microbiota. One type of drinking water was untreated, while the other type was daily treated with sodium dichlorocyanurate (50 mg/L). A total of 240 broiler chicks were divided into 2 groups based on their initial body weight. There were 6 replicates in each group, and each replicate cage contained 20 birds. Each cage was assigned to a different floor of the battery cage. On the final day, water samples were collected from each replicate cage at the opening of the drinking cup height, and one bird was selected from each replicate cage to obtain cecal content samples for measuring microbiota composition using the 16S rRNA technique. We found that drinking water treated with sodium dichlorocyanurate significantly reduced the richness and diversity of microbiota and diminished/disappeared most gram-negative bacteria. Broiler chicks that consumed chlorinated drinking water exhibited changes in the composition of cecal microbiota, with Alistipes serving as the marker species in the cecal content of broiler chicks that consumed untreated water, whereas AF12 served as the marker species in the cecal content of broiler chicks that consumed chlorinated drinking water. Functional prediction using the MetaCyc database and species composition analysis of metabolic pathways showed that changes in 7 metabolic pathways were related to the abundance of Providencia. Therefore, we concluded that chlorinated drinking water reduced the bacterial load in drinking water, thereby altering the cecal microbiota composition and regulating the metabolic activity of broiler chicks.