Display omitted •Solve the defect of cinnamaldehyde that are easy to volatile and lose during use.•Fixing cinnamaldehyde essential oils on wood using Schiff base reaction.•The treated wood is resistant to decay while being environmentally friendly. Environmental concerns over organic chemicals used for protecting wood and wood products from biological degradation have prompted the development of natural wood preservatives with lower health risks and prolonged efficacy. In this study, mixing chitosan and cinnamaldehyde to prepare an emulsion as natural wood preservative can effectively infuse cinnamaldehyde in the treated wood, enhancing the ability of the wood to resist decay fungi. Wood decay fungi were cultivated in emulsion with various molar ratios of cinnamaldehyde to chitosan emulsion. The antifungal property of the emulsion was compared according to its growing colony diameter and the mycelial morphology. The preservative emulsion was also impregnated into poplar (Populusnigra L.) with vacuum-pressure cycle. The decay resistance was evaluated by wood decay resistance test and electron microscope observation. The results showed that the cinnamaldehyde chitosan emulsion severely impacted the normal growth of the decay fungi and changed the mycelium morphology of the decay fungi. The Schiff base was formed in treated wood, and the decay resistance of treated wood was improved. Its decay resistance against brown-rot fungi Gloeophyllum trabeum was better than that of white-rot fungi Trametes versicolor. This study suggests the cinnamaldehyde chitosan emulsion can be effectively used as environmentally friendly wood preservative.