The new different-speed mixer is widely used in the production of hydrofluoric acid, amino plastics, synthetic rubber and so on. The stirring kneader shafts are the key parts of different-speed mixer, and the problems about strength of shafts were very important. The finite element model of the stirring kneader shaft was built based on ANSYS software in this paper. The ANSYS software was adopted for the static strength analysis of the stirring kneader shaft, and the dangerous points were found. Then these data were used to perform a fatigue analysis by ANSYS-Fatigue. The results showed that the new stirring kneader shaft was able to meet fatigue requirement during the whole service life.