Chitosan nanoparticles loaded with cinnamon essential oil (CE-NPs) exhibited the excellent antimicrobial and antioxidant property for the pork during refrigerated storage. In this study, CE-NPs with three sizes of 112 nm, 215 nm and 527 nm were prepared by ionic gelification reaction. The loading capacity of cinnamon essential oil was improved with the mean diameter of CE-NPs increasing. The fresh pork was wrapped with the low density polyethylene (LDPE) films and the active films coated with different CE- NPs and displayed at 4 C for 15 day. The active films with 527 nm CE-NPs led to a significant decrease of microbial growth, pH, peroxide value (POV), 2-thiobarbituric acid (TBA) and sensory scores of the pork (P < 0.05) than the other treatments at the end of storage. The 527 nm-treated pork samples showed significantly highest redness (P < 0.001) in all the four groups. In all, CE-NPs with the big size have more potential as a natural preservative to maintain the quality of meat and meat products.