Totally 24 Gannan yak were slaughtered at 0~4℃, wind speed 0.5m/s conditions to aging , then the shear force, MFI and apoptotic enzymes activity were determined during postmortem aging. Results from this research show that the shear force values of TB, ML and SM decrease by 35.6%, 27.4%, 33.5%, and the MFI values increase by 69.7%，65.7 %，63.0%. This investigation also indicated that TB and SM at 1d postmortem aging caspase-3 activity reach the highest value (P<0.001), while ML at 10h postmortem aging caspase-3 activity reaches the highest value; caspase-8 activity reaches the highest value activity (P<0.001) at 5h postmortem aging, and the caspase-8 activity of TB and SM reach highest value earlier than ML; at 5h postmortem aging, caspase-9 activity is significantly higher than that at 0.5h postmortem aging(P<0.001), at the same time caspase-9 activity reaches the highest value in ML and SM muscles, while the caspase-9 activity of TB reaches the highest value at 10h postmortem aging, it is 2.39 times than its initial value; the caspase-3 and caspase-8 activity is related to shear force and MFI significantly (P＜0.01), while caspase-3, caspase-8 and caspase-9 activity show significant correlation with each other (P＜0.05).