To explore the role of resistant starch in fermented milk， RS2 type potato resistant starch （G） and microwave-wet heat method were used to prepare RS3 potato resistant starch （W）， and their content and morphology during fermented milk processing and storage were observed. The change was observed. The fermented milk without added resistant starch was used as a control to observe the microstructure and analyze the rheological properties and stability of the fermented milk gel process. The results showed that the residual amount of W relative to G was higher and maintained at about 60%； both resistant starch retained the morphology of starch granules， but there were different degrees of loss， mainly concentrated in the late fermentation and storage period. W was more helpful for the fermented milk to form a complete and uniform microstructure； the fermented milk containing W had strong micro-elasticity and contributed to the combination of casein particles to form a more robust structure； the micro-stability of the fermented milk containing W was superior to that of fermented milk containing G.