The unbalanced carrier shaft leads to vibration, affecting crushing effects. To avoid vibration and reduce the weight of the carrier shaft, the position of the SG4390 plastic granulator carriers was readjusted, and strength of the danger cross section of the improved carrier shaft was checked. Finite element static analysis and dynamic analysis of the improved carrier shaft were carried on by ANSYS Workbench, while the natural frequency was unchanged, compared with the old structure, and the improved carrier shaft had not stress concentration. The experiment of carrier dynamic balance testing was done by hard support balance machine for the improved carrier shaft, it was shown that the balance of the carrier shaft was unchanged. The results show the new structure of the carrier shaft can not only decrease the weight,but also make the carrier shaft force uniformly.