The indicators about ageing mechanism including pH value, content of glycogen, myofibril fragmentation index (MFI), the activities of calpains and cathepsin L and meat quality including pressing loss, cooking loss, shear force and chromaticity during ageing of eight days were determinated from ten Qinghai yaks. The correlation between shear force and MFI, activities of calpains and cathepsins L were also analyzed. The results showed that the all above mentioned indicators changed during the ageing period, and the direct reflect was improving the yak meat tenderness. MFI had a very significantly（P＜0.01）correlated with the activities of calpains, and had a significantly correlated with the activity of cathepsin L（P＜0.05）, while there was a significant negative correlated with the activity of cathepsin L（P＜0.05）.