The study presents a rigorous methodology based on the weighted TOPSIS method to systematically determine the optimal topology of the amphibious vehicle framework, aiming to achieve the dual objectives of reducing overall weight while ensuring the structural strength and stiffness of the body. This research further involves the comprehensive testing and evaluation of the effectiveness of this methodology, particularly in contrast to optimization approaches based on universal programs. To exemplify this methodology, we apply it to the optimization of the Humdinga amphibious vehicle as a case study. Firstly, this approach provides a rational frame topology based on pre-study results of body structure response under extreme operating conditions. Subsequently, topological optimization is carried out, entailing the removal of elements with minimal impact, and parametric optimization, encompassing the redistribution of the mass among frame elements. This process employs the TOPSIS method, facilitating the determination of the optimal topology and parameters for the frame and panels. The underbody weight was reduced by 44.7%. In comparison with the outcomes obtained through topology optimization in a widely-used software program like Hypermesh, the reduction in the number of connection points stands at 42%. Additionally, the overall strength of the underbody has increased by 4.3%, while the middle and rear sections exhibit an even more impressive improvement, with strength enhancements 6.9%. The presented methodology enables topological optimization of frame elements with considering of connection technologies to enhance overall performance. Additionally, the proposed technique exhibits reduced dependence on subjective researcher factors, as compared to conventional topological optimization methods found in universal software, thereby minimizing the need for interpretation.