Abstract: In order to research the physical properties changes of the Tibetan kefir fermented milk, this paper measured the pH value, water-holding capacity (WHC) , syneresis, viscosity, lactose content and protein content at different incubation temperature and time. By using the SAS statistical software, we analyzed the variation of the six indicators during the fermentation process, and explained the reason of the regulation. After scanning by the scanning electron microscopy (SEM) , showing the structural difference between Tibetan kefir fermentation and ordinary yogurt intuitively, and explaining the reason why the time -viscosity curves had such a large difference between Tibetan kefir fermentation and ordinary yogurt. Tibetan kefir fermentation had no complex space structure compared with merchant yogurt from the picture scanned by SEM. The six physical properties were influenced by the fermentation temperature and time and the interaction effect at different levels.