Abstract: Nitric oxide (NO) is a gas signaling molecule with high bacterial inhibition rate, which has been widely used in biomedical treatment. However, there are still problems such as poor biocompatibility of NO donor materials, low NO load, poor control release and slow-release effect. In this study, we used an aquatic polysaccharide material, sodium alginate (SA), to prepare sulfhydryl sodium alginate (SA-SH) and NO donor S-nitroso sodium alginate (SA-SNO), and prepared in-situ formed hydrogel by using different ratios of SA-SH and SA-SNO. The results show that the NO loading in the hydrogels increased with the increasing content of SA-SNO, and the release curve indicates that the gel possessed long-lasting release effects, wherein the releasing amount of NO arrived to 30.12−44.32 μmol·g⁻¹ even after 5 d and the total release amount was 152−264 μmol·g⁻¹. Additionally, antibacterial experiments show that the hydrogel had a significant inhibitory effect on Staphylococcus aureus and Escherichia coli. In summary, the composite hydrogel has the potential application as an anti-bacterial wound dressing.