The work aims to improve the microbiological influenced corrosion resistance of Zn-Ni alloy coatings. 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) was added into sulfate electrolyte. DCOIT composited Zn-Ni alloy coatings were obtained on carbon steel by cathodic galvanostatic electrodeposition. By potential monitoring and current efficiency calculation, the influence of DCOIT on electrodeposition was evaluated. Further, scanning electron microscopy, energy- di-spersive X-ray spectroscopy and X-ray diffraction were performed to study the effect of DCOIT on morphologies, structures and Ni contents of the composited Zn-Ni alloy coatings. Then, the Fourier transform infrared spectroscopy and fluorescence mi-croscopy observation were used to verify the existence of DCOIT and the antibacterial effect of the composite coatings. At last, the pH and bacterial concentration variations were monitored by exposing the DCOIT composite Zn-Ni alloy coatings in sul-fate-reducing bacterial (SRB) medium and the corrosion rates of the coatings were calculated to evaluate the corrosion resistance of coatings in SRB medium. During the electrodepositing process, DCOIT was absorbed on the depositing surfaces, which led to negative electrodepositing potential shifts and decreased current efficiency. The addition of DCOIT dramatically influenced the morphology, structure and Ni contents of the coatings. The Ni content showed a linear growth relationship with the DCOIT adding concentration, leading to crystalline phase transformation. After electrodepositing, DCOIT existed in the composite coatings with effective molecular structure and showed antibacterial properties successfully. When 2 mmol/L DCOIT was added, the coating showed the largest compound quantity and the best antibacterial properties. Finally, the DCOIT composite Zn-Ni alloy coatings effectively inhibited the growth and metabolism of SRB, thus reducing corrosion rates and enhancing corrosion resistance. DCOIT can be successfully composited into Zn-Ni alloy coating, which effectively improves antibacterial properties and enhances corrosion resistance in SRB medium.