With the aim to investigate apoptosis-inducing-factor (AIF)-mediate apoptosis and mechanism of lysosomal cathepsins involved in AIF activation of bovine muscle during postmortem aging, six healthy Simmental crossbreeding local yellow cattle were slaughtered and longissimus thoracic muscles were removed from the carcasses then aged at 4℃ for 6h, 12h, 24h, 72h, 120h and 168h. At the end of each storage period, ROS content, lysosomal membrane stability, cathepsins activities, mitochondrial membrane permeability, the expression of AIF and nuclear morphology were measured. The results suggested that ROS content was decreased from 0h to 6h, but it was significantly increased from 6h to 168h during postmortem aging (P<0.05). Lysosomal membrane stability was significantly decreased from 0h to 168h (P<0.05). Cathepsin B, D and L activities were increased as the postmortem aging was increased (P<0.05). Mitochondrial membrane permeability was significantly increased during postmortem aging (P<0.05). The AIF level in mitochondria was significantly increased from 0h to 12h and decreased as the postmortem aging was increased, the amount of AIF in the nucleus was increased during postmortem aging (P<0.05). The volume of cell nucleus was gradually increased and some nucleus were dissolved and broken during bovine postmortem aging. It was concluded that the generation of ROS may lead to imbalance of lysosomal membrane stability, and then cathepsins were released to cytoplasm. Subsequently, the mitochondrial outer membrane was permeabilized, and AIF was translocated to the cytosol and nucleus, where it induced apoptosis of nucleus.