Abstract: This study investigated whether beef tenderization during post-mortem ripening depends on anti-apoptotic protein(Bcl-2)and whether there is a significant difference in beef tenderness among different parts. In this paper,the Bcl-2,pro-apoptotic protein(Bax)and apoptotic enzyme expression levels were measured during the post-mortem maturity of beef,and the relationship between it and the shear force value of beef was analyzed. The mechanism of the relative content of Bcl-2 and Bax on beef tenderization was finally determined. At 2~12 h postmortem,the relative contents of Bax/Bcl-2 and the activities of apoptosis enzyme(Caspase-3,Caspase-8 and Caspase-9)in anterior triceps brachii muscle(TB),midbrain longissimus muscle(ML),hindquarters semimembrane muscle(SM)increased significantly(p<0.05),shear force decreased significantly(p<0.01)at 6~48 h after slaughter. The study pointed out that the tenderness of beef depends on the mitochondrial pathway and the death receptor pathway. The Bcl-2 protein regulates the tenderness of beef through Caspases cascade reaction. The increase of the relative content of Bax/Bcl-2 leads to the release of Cyt-C from mitochondria to the cytoplasm,initiates the Caspase cascade,activates Caspase-3 to hydrolyze myofibrillar protein,and triggers apoptosis. As a result,the tenderness of beef continued to increase within 48 h after slaughter,and the tenderness of ML was better than that of TB and SM.