Objective To investigate the protective effects and possible mechanism of pigment epithelium derived faetor (PEDF) on myocardial cells H9C2 under hypoxia and serum-free condition.Methods H9C2 cells were culture in vitro and performed the hypoxia and serum-free processing.The cells were divided into the control group (H9C2),hypoxia group (hypoxia + H9C2),PEDF group(hypoxia+H9C2 +PEDF) and mitochondrial fission inhibitor(Mdivi-1) group(hypoxia+h9C2+Mivi-1).The apoptotic rate was detected by TUNNEL staining.The proteins levels of dynamin related peptide1 (Drp1) and cleaved-caspase 3 were measured by Western blot.Electron Microscopy and MitoTracker Red were used to detect the mitochondria morphology,the mitochondrial membrane potential was evaluated by cationic dye JC-1.MitoSOXTM was used to detect mitochondrial reactive oxygen species (ROS).Results Hypoxia induced mitochondrial fission(P＜0.05).The hypoxia group (6 h) and control group had statistical difference(P＜0.05).PEDF reduces mitochondrial fission under hypoxia condition(P＜0.05),which had statistical difference between the PEDF group and hypoxia group (6 h)(P＜0.05).PEDF and Mdivi-1 could decrease cell apoptosis under hypoxia condition(24 h),compared with the hypoxia group,the difference was statistically significant(P＜0.05).Conclusion PEDF decrease cell apoptosis by inhibiting H9C2 cells mitochondrial fission under hypoxia condition.