Abstract: The objectives of this study were?to investigate rheological properties of cow milk and goat milk during lactic acid fermentation. Cow milk and goat milk were lactic acid fermented for 6 h respectively. Shearing viscosity, acidity, and protein content were measured at 0, 1, 3 and 6 h respectively. The results showed that shearing viscosity and protein content of cow milk were higher than that of goat milk at 0, 1, 3 and 6 h. But acidity of goat milk were higher than that of cow milk at the same time. Protein is an important affecting factor on rheological properties of cow milk and goat milk.