Abstract: Casein in yak milk was modified by acylating reagents and transglutaminase( TG),and modified casein was analyzed for their heat stability.Spectrophotometry at 280 nm was uesd to determine the size of the casein heat stability.The results showed that the heat stability of casein greatly increased after modification of transglutaminase( TG) cross- linking. After using different acylating reagents modification,the heat stability of casein increased.Different modified casein heat stability showed a great difference,succinic anhydride modified casein had the strongest heat stability. The results could provide a reference basis for yak casein modification and product development.