To investigate the antibacterial activity of commercial organic acid Activate WD (WD), the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of WD against Staphylococcus aureus, Escherichia coli, Salmonella pullorum, and Campylobacter jejuni were determined by double broth dilution method. Bacteria were added in a mixture of water and commercial broiler feed adjusted by WD into pH 3.0, 4.0, and 5.0; the survival of bacteria was determined by a direct plate count method at 0, 0.5, 1, 4, 8, and 24 h after being mixed to test the bactericidal potential of WD. The results showed that the MIC of WD against four bacteria was 0.3125%, and the MBC was 0.625%. At pH 3.0, bacteria could not survive. Campylobacter jejuni died after 4 h of incubation at pH 4.0, 5.0, whereas for other three bacteria, the bacterium numbers were below detection limits until 8 h of incubation. In conclusion, WD had significant antibacterial activity, and could be used on farms to prevent cross-infection via rearing water.