A g-C₃N₄/ZnO/cellulose ternary composite (labeled as CNZCel) with an ordered structure and excellent antibacterial properties has been successfully synthesized via a facile method. Its morphology, microstructure and components have been analyzed by using XRD, SEM, TEM and EDS, and the results corroborate the co-existence of three components in the ternary composite. It is revealed that ZnO particles are connected to the layered g-C₃N₄ and simultaneously attached to the cellulose substrate. This microstructural feature is also borne out by the relativistic density functional study of a finite g-C₃N₄–ZnO–cellulose cluster. Both experimental and theoretical results unravel that the interfacial bonding interactions in the ternary composite improve electron transfer among components and enable high-efficiency spatial separation of photogenerated electrons and holes. Consequently, good antibacterial performance of the composite has been found in tests. This study provides the prospect of preparing low-cost and environment-friendly food packaging materials, which are also endowed with excellent antibacterial activity.