GeSn alloy, as a novel silicon-based optoelectronic material, exhibits significant application potential in the field of infrared photonics due to its tunable bandgap properties and compatibility with silicon-based CMOS processes. Although the experimental performance of GeSn laser under low-temperature conditions has been preliminarily validated, the optimization and practical application of this device still face challenges such as insufficient understanding of material properties. This work addresses issues such as the unclear carrier dynamics mechanisms in GeSn alloy applications in infrared photonics. A theoretical model integrating band parameters, non-equilibrium carrier transport, and radiative recombination is proposed to systematically investigate the mechanism by which thermal excitation and phonon-assisted processes influence the direct-band spontaneous emission in GeSn alloys under variable temperature conditions. The results indicate that the carrier transfer process between the Γ_CBM and L_CBM energy bands of GeSn alloy exhibits significant composition dependence: for low-Sn-content GeSn alloy with Sn content below 10%, temperature-induced L_CBM→Γ_CBM electron transfer dominates, leading to an increase in direct band emission efficiency with temperature rising, whereas in high-Sn-content GeSn alloys with Sn content between 10% and 20%, the Γ_CBM→L_CBM electron escape process is more pronounced, resulting in a decrease in direct band emission efficiency with the increase of temperature. A modified Arrhenius model of the carrier dynamics competition further indicates that thermal excitation and phonon scattering synergistically regulate electron transfer between Γ_CBM and L_CBM. The analysis based on the modified Arrhenius model further indicates that both thermal excitation and phonon-assisted processes promote the injection and escape of electrons in the Γ_CBM valley, acting as key factors in modulating the radiative recombination efficiency at the direct bandgap of GeSn alloy. The red shift of the peak position in the spontaneous emission spectrum of GeSn alloy is mainly due to the bandgap contraction effect; At the same time, phonon-assisted processes reduce the dispersion of carrier energy distribution, leading to a pronounced narrowing effect in the direct band emission spectrum. The quantitative findings further elucidate the mechanism by which thermal excitation and phonon-assisted processes influence the direct bandgap luminescence of GeSn alloy, providing theoretical guidance for the performance regulation of infrared optoelectronic devices.