Abstract: OBJECTIVE To use cultured neonatal rat cardiomyocytes with hypoxia- reoxygenation(H/R) to mimic in vivo ischemia-reperfusion injury (I/R), and to investigate the mitochondrial protective mechanism of Fuzi polymccharide postconditioning in cardiomyocytes against hypoxia-reoxygenation injury. METHODS Rat myocardial cells were divided into four groups: control, H/R, postconditioning and Fuzi polymccharide postcondition groups. The cells in H/R group were incubated primarily in hypoxic buffer solution for 3 hours, thereafter, these cells were incubated for 6 hours in normal culture medium. The cells in postconditioning group were given tree cycles of 5 min reoxygenation and 5 min hypoxic prior to 6 hours of reoxygenation. The cells in Fuzi polymccharide postconditioning group were cultured in medium added with 10 g·L^-1 Fuzi polymccharide for 6 hours after 3 hours of hypoxia. Cell apoptosis of cardiomyocytes and mitochondrial membrane potential of cardiomyocytes were measured by flow cytometry. AIF was detected by Western blotting. The SOD activity and MDA content within cardiomyocytes were measured. RESULTS Compared with H/R group, Fuzi polymccharide postconditioning protected the SOD activity, reduced production of MDA, kept mitochondrial membrane potential of cardiomyocytes stable, depressed the translocation of AIF from mitochondria into cytosol, and decreased the cell apoptosis. CONCLUSION These data suggest Fuzi polymccharide postconditioning can protect cardiomyocytes from H/R injury. The mechanism is related to its antioxidation and protection on mitochondria.