The work aims to verify that the main stressed component (rotating shaft) of the sealing mechanism meets the needs of the actual working conditions. Based on the design of the overall layout for a bag forming packaging machine and the design scheme and the theoretical calculation of the sealing mechanism, the 3D modeling of the corresponding sealing mechanism was completed. Then, the static analysis and modal analysis thereof were carried out with Ansys Workbench and the fatigue analysis was conducted by fatigue analysis software nCode DesignLife. The maximum stress on the surface of the rotating shaft was 29.94 MPa, the natural frequency was more than 1246.6 Hz, and the life of most parts of the shaft was more than 1.127×108. The results show that it can meet the requirement of theoretical design, work normally in the actual working conditions, and will not produce resonance and safety fatigue. The location of fatigue failure can be forecasted according to the simulation analysis.