The change of protein content will affect the characteristics of fermented milk， and then determine the quality of fermented milk. In this study， the effects of protein content of 2.4%， 2.8% and 3.2% on the micro-rheological properties of fermented milk during fermentation were analyzed by multi-frequency diffusion spectroscopy， and the texture characteristics and stability of fermented milk with different protein content during storage were analyzed， and sensory evaluation was also made. The results of micro-rheological analysis showed that the milk gel formed by the increase of protein content had higher solid-liquid equilibrium value and lower elastic factor， and had no effect on flow factor， but the time to reach gel point was shorter， which shortened the fermentation time. It was speculated that the increase of protein content accelerated the aggregation of casein particles. At the end of fermentation， the viscosity factor of fermented milk with protein content of 2.8% was the highest. During storage， the viscosity， consistency and cohesion of fermented milk with protein content of 2.8% were significantly higher than those of the other two groups (P<0.05)， and the texture state was the best. The water holding capacity of fermented milk with protein content of 2.4% was significantly lower than that of protein content of 2.8% and protein content of 3.2% (P<0.05). The pH value and titration acidity increased with the increase of protein content， and the pH value and titration acidity of fermented milk in three groups changed uniformly (P>0.05)， but the pH value of 3.2% protein group was always higher than the other two groups， and the higher the protein content， the higher the titration acidity. Sensory evaluation showed that the scores of fermented milk with protein content of 2.8% and 3.2% were close to each other， which was better than that with protein content of 2.4%. This study provides data support and theoretical reference for the development of fermented milk with different protein content， and has certain guiding significance for the development of diversified fermented milk products.