Truck-beam landing gears usually face vertical velocity distortion of the drop test basket during traditional reduced-mass method drop tests， leading to deviations in dynamic response. Aiming to enhance test accuracy and engineering applicability， this study proposes a multibody dynamics model of the truck-beam landing gear. The drop response characteristics under both the reduced-mass method and the lift-loading method are compared and analyzed， revealing the inherent mechanism of the traditional method： The continuous post-touchdown acceleration and velocity overshoot due to the absence of lift simulation. An improved approach based on parameter feedback iteration is proposed， achieving simultaneous equivalence in velocity and energy through coordinated adjustment of the release mass and height. Simulation validation conducted on a main landing gear of a large civil aircraft demonstrates that the proposed method reduces the error in the basket’s vertical velocity from 11.15% to 0.13%， confines the energy error within 2.34%， and narrows the discrepancy in key load indicators （e.g.， peak oil damping force） to 4.01% compared with the lift-loading method. The results indicate that the proposed method significantly enhances the accuracy and reliability of drop tests for truck-beam landing gears without introducing complex lift simulation systems， providing an efficient engineering solution for validating landing gear buffer performance.