Objective: To investigate the protective effect of ω-3 polyunsaturated fatty acid (ω-3PUFA) on the remnant liver in rat with partial hepatectomy and its mechanism. Methods: Male SD rats were randomly divided into sham operated control group, model group (partial hepatectomy + normal saline), low dose ω-3PUFA treatment group (partial hepatectomy + 1 mL/kg ω-3PUFA) and high dose ω-3PUFA treatment group (partial hepatectomy + 2 mL/kg ω-3PUFA). The histopathological change of the remnant liver was dynamically assessed by light microscope at day 1, 2, 3 and 5 after surgery. In addition, the expression of occludin protein and the ultramicrostructural features of the hepatic cells were examined at day 3 after surgery. Results: The histopathological findings showed that the hepatic cells and histological structures were severely damaged, while the pathological changes of the two doses of ω-3PUFA treatment groups were of markedly lesser degree but no obvious difference was noted between themselves. The expression levels of occludin protein of the two doses of ω-3PUFA treatment groups were markedly higher than that of the model group, but were similar between themselves. The electron microscopic observations revealed that the tight junctions between hepatic cells were severely disrupted, while these structures of the two doses of ω-3PUFA treatment groups were maintained relatively intact, and the high dose group was better than that of low dose group in this respect. Conclusion: The perioperative administration of ω-3PUFA can increase the occludin expression and preserve the ultramicrostructures of hepatic cells in rat with partial liver resection, which may be responsible for its effect of hepatic barrier protection.