Nitric oxide (NO) is an endogenous gas molecule which played a key role in wound healing process due to their beneficial effects on inflammation, cell proliferation and remodeling. However, the clinical application of NO is limited due to their burst and short half-life release. To overcome this, copper ions (NO-generating catalyst) was incorporated in the gelatin-based hydrogel (GH/Cu) for in situ release of NO in the presence of endogenous S-nitrosothiol. GH/Cu hydrogels presented the sustained release of NO for over 2 weeks within the physiological level (0.5-4×10-10mol/cm-2/min-1), which stimulated the macrophage polarization from M1 (pro-inflammatory) macrophage to M2 (anti-inflammatory) macrophage. Overall, these results confirm the pro-wound healing activity of GH/Cu and showed that GH/Cu is the promising material for wound treatment. Acknowledgements: 2019R1A6A1A11051471, NRF-2018R1A2B2004529