Objective To study the effect of histidine kinase gene envZ in two-component system ompR/envZ on biofilm formation ability of avian pathogenic Escherichia coli (APEC), understand the regulation mechanism of the two-component system on biofilm of APEC, and provide a reference for investigating the ways of biofilms affecting APEC antibiotic resistance.Method The red homologous recombination method was used to construct the envZ-gene-deleted strain, and the differences in growth characteristics and biofilm formation abilities between wild strain and the envZ-gene-deleted strain were compared. The mechanism of envZ regulating biofilm formation related genes in transcriptional regulatory network was analyzed by transcriptomics.Result The envZ-gene-deleted strain AE17ΔenvZ was successfully constructed. The envZ gene deletion had no significant effect on growth rate of APEC, but weakened the APEC biofilm formation ability. Compared with wild strain AE17, AE17ΔenvZ had 711 differentially expressed genes, and the genes related to biofilm formation were significant down regulation.Conclusion In addition to responding to environmental osmotic pressure, envZ gene is also involved in regulating the formation of APEC biofilm.