The work aims to develop and design a clamp mechanism, the key part in blowing, filling and sealing integrated machine for plastic bottles and analyze and verify the design rationality of the clamping mechanism, so as to provide support for high-intensity clamping operation. The clamping mechanism was designed to meet the integrated functions of blowing, filling and sealing. The finite element numerical simulation method was used to analyze the mechanical strength and displacement of the designed clamping mechanism components during operation. The stress at the contact part of the support shaft of the clamping structure was large, and the strength of the support shaft was improved by changing the material 2Cr13 to 3Cr13. At the same time, the structure of the clamping support shaft was optimized to improve the stress distribution at the contact part. The finite element numerical simulation results showed that the maximum equivalent stress at the contact part of the support shaft was 394.13 MPa, which was 36.95% lower than that of the original model, and met the structural strength requirements. The stress concentration at the transverse contact part between the clamping support shaft and the middle positioning plate in the middle of the clamping mechanism is the weak link in structural design. The finite element numerical simulation method can quickly and accurately analyze the structural strength of the clamping mechanism, and improve the design through iterative optimization to ensure the reliability and stability of the clamping mechanism. The designed clamping mechanism has high precision and stable operation, which meets the design requirements.