Abstract: Sodium carboxymethyl cellulose( CMC- Na)- based nanocomposite films with natural antibacterial cinnamaldehyde and different contents of nano- montmorillonite( MMT) were fabricated by film- casting method.The effects of MMT content on mechanical properties,water vapor transmittance,transparency,cinnamaldehyde release ability and antimicrobial properties of the films were studied. The results showed that the tensile strength and elongation at break of the were film increased first and then decreased with the increase of MMT content,and the tensile strength reached the maximum at 4% MMT content.Water vapor transmittance and transparency were reduced gradually with the increase of the MMT content. MMT was good barrier to the diffusion and release of cinnamaldehyde in film.The CMC- Na films containing MMT maintained high antibacterial activity with the extension of storage time,and the antibacterial activity of films without MMT was reduced greatly because more cinnamaldehyde volatilized. Conclusion: nano montmorillonite can effectively control the release of cinnamon in CMC- Na film.