Abstract <p>Generalized wave impedance theory, used to simplify stress wave analysis, has practical limitations. This study examines its applicability under non-ideal conditions, specifically the influence of coupling factors on wave propagation at variable cross-sections via simulations. Based on the generalized wave impedance theory, this study investigates the influence of coupling factors in generalized wave impedance on stress wave propagation characteristics at variable cross-sections through simulation analysis. The research reveals that under constant generalized impedance, a larger cross-sectional area ratio reduces the error between theory and simulation for reflected waves but increases it for transmitted waves. Analyzing the influence of the area ratio, wave impedance ratio, density, Young’s modulus, and sound speed on transmitted and reflected waves showed that the area ratio is the primary factor affecting the accuracy of the generalized wave impedance. Maintaining the same area ratio while altering the density and Young’s modulus ratios (changing wave impedance) revealed that accuracy improves with increasing amplification coefficients. Sound speed, as a coupling factor of density and Young’s modulus, had minimal impact on accuracy. The findings not only contribute to improving the theoretical foundation of Split Hopkinson Pressure Bar (SHPB) experiments but also offer new perspectives for enhancing the accuracy of material parameter measurements.</p>