Update Publication. Transcription regulatory factors of MarR family play an important role in diverse bacterial physiologic functions, whereas the effect and its intrinsic regulatory mechanism on aquatic pathogenic bacteria Aeromonas hydrophila are still largely unknown. In this study, we firstly constructed a deletion strain of gene AHA_2124 (ΔAHA_2124) of a MarR family transcriptional regulator in A. hydrophila, and found that it had significantly enhanced hemolysis, extracellular protease, and motility activities. The differentially expressed proteins (DEPs) between wild-type and ΔAHA_2124 strain were compared by using the label-free based quantitative proteomics technology, and there were 178 DEPs including 80 proteins up-regulated and 98 proteins down-regulated. Bioinformatics analysis showed that the deletion of gene AHA_2124 led to some changes in the expression of proteins related to multiple biological processes, such as translation, peptide transport and oxidation reduction. These results provided a theoretical basis for better exploring the regulatory mechanism of transcriptional regulators of the MarR family of A. hydrophila on bacterial physiological functions.