Abstract: Objective To study the effect of apocynin on oxidative stress injury of primary atrial cells in rabbits by establishing a primary atrial cell injury model of rabbits with low-consistence H₂O₂. Methods Eighteen rabbits were randomly divided into normal control group,H₂O₂ group and apocynin group.All atrial cells were primarily cultured.In H₂O₂ group,100μmol/L H₂O₂ was added into cultured primary cells and cultured for 2h.In H₂O₂ group,100μg/ml apocynin was added into cultured primary cells and cultured for 1h,into which 100μmol/L H₂O₂ was added and cultured for 2h.Finally,changes in oxidant and anti-oxidant indexes were detected. Results The activity of superoxide dismutase（SOD） and glutathione hormone（GSH） level were significantly lower while the malondialdehyd（MDA） and intracellular free calcium levels as well as the expression level of nicotinamide adenine dinucleotide phosphate（NADPH） p22phox were significantly higher in H₂O₂ and apocynin groups than in normal control group（P＜0.05）.The activity of SOD and GSH level were significantly higher while the MDA and intracellular free calcium levels as well as the expression levels of NADPH p22phox and mitochondrial mRNA were significantly lower in apocynin group than in H₂O₂ group（P＜0.05）. Conclusion Apocynin can protect primary atrial cells against injury by inhibiting NADPH oxidase.