The temperature of reusable rockets has been steadily increased, and their structural design is subjected to stringent thermal environment assessments. Currently, numerical simulations are considered one of the effective tools during the design phase of spacecraft. However, the mechanisms of thermal effects caused by airflow on the rocket's surface and the ground during the launch phase are not yet well understood. Therefore, the ground launch process of a particular reusable rocket was investigated through the employment of dynamic boundary computational fluid dynamics (CFD) techniques and a multi-component model, through which a dynamic numerical simulation was conducted to analyze the development of high-temperature exhaust gases and their impact on the thermal environment of both the ground and the rocket body. The results demonstrate that during the early stage of launch at near-ground positions, the ground is continuously subjected to a cold-wall heat flux exceeding 2.5 × 10⁷ W/m², with convective heat transfer being identified as the dominant mode. The maximum convective heat flux density and radiative heat flux density at the bottom of the rocket body are found to reach 35 000 W/m² and 60 000 W/m², respectively. After the rocket is lifted off, both the convective heat flux density and radiative heat flux density are observed to decrease with increasing altitude, with radiative heat transfer being established as the dominant mode at this stage.