When laparoscopic surgery is performed, polymer clip blood vessel ligators are widely used to prevent bleeding and secure surgical vision. However, long-term use of such ligators can cause many structural problems, especially in the jaw part where the clip is mounted directly to the blood vessel. For example, jaws of the ligation device might be opened above the design value and upper and lower jaws might be twisted against each other. In addition, buckling or bending deformation can easily occur at the tip of the inner shaft. Due to these problems, the ligation machine cannot ligate the clip properly, which might lead to a medical accident. Therefore, in this study, the design was changed to improve these problems by increasing the pin diameter and contact surface, applying a double pin structure, and changing the structure of the shaft tip. As a result, the modified model showed 12.5% and 10.2% improvements in opening and twisting stiffness compared to the initial model with 7.2% and 58% improvements in critical buckling load and bending stiffness, respectively.