Abstract: To meet the requirements of quantitative evaluation and precise regulation of radiative characteristics of solid rocket motor tail flames, a simplified chemical reaction mechanism for plume afterburning was adopted. The mechanism couples a gas-solid two-phase combustion flow model with numerical methods for radiative transfer calculation. The study systematically investigates optimization methods for the plume computational domain. To address the wide spatial span of the plume flow field, a selection criterion based on the differential of velocity and temperature excess parameters is adopted to reveal the influence of flight altitude and Mach number on the minimum computational domain boundaries. Comparative validation between two-dimensional axisymmetric and three-dimensional full-scale models verify the applicability of simplified physical models for processing two- phase plume radiation simulation. On this basis, a cross-comparative study is conducted to analyze the plume characteristics of three propellant systems under typical flight conditions, namely four-component hydroxy-terminated polybutadiene, nitrate ester-plasticized polyether and glycidyl azide polymer. The results indicate that the plume afterburning process produces a prominent homogenization effect on compositional differences between different propellant formulations, which attenuates the radiation suppression effect relative to thermodynamic predictions at nozzle exit. For the HTPB and NEPE systems, every 2% increase in HMX mass fracture reduces the peak radiation intensity by 2.33% and 3.40% respectively, the NEPE system exhibits higher sensitivity to HMX content variation. By fundamentally modifying fule gas composition, the GAP-based propellant achieves a 26.83% reduction in radiation intensity for per 10% increase in GAP mass fracture while maintaining excellent energy performance. These conclusions provide a quantitative theoretical basis for the formula design and signature optimization of low-observable solid propellants.