Abstract: The change of the heat stability of yak’s skim milk, emulsifying properties and turbidity had been studied in accordance with the rise of temperature and time. Meanwhile, the change of surface hydrophobicity and average particle size of the casein micelles in the solution in this process was also studied. As a result, with the temperature and time rose, the heat stability of skim milk went down, emulsifying dropped, turbidity went up, surface hydrophobicity and average particle size of casein increased in the overall. When the skim milk was above 70℃ and heating time was more than 15min, the change was remarkabled. The results provided some theoretical basis for the processing of casein in yak milk.