Abstract: Based on computational fluid dynamics (CFD) technology and combined with the discrete ordinates (DO) radiation model, the surface solar radiation distribution of the electronic device cabin of a certain type of near space vehicle and its influence on the heat dissipation process inside the cabin are investigated. A three-dimensional thermal simulation model is established to compare and analyze the forced air cooling heat dissipation characteristics under two extreme conditions: ground high-temperature and normal-pressure condition (environmental temperature 45 ℃) and 20 km high-altitude low-pressure condition (environmental temperature −45 ℃, pressure 5.5 kPa). Numerical simulation results indicate that under normal-pressure condition, the highest temperature inside the cabin reaches 62.82 ℃. Under low-pressure condition, although convective heat dissipation efficiency decreases due to reduced air density, the low-temperature environment compensates for the heat load, and the highest temperature inside the cabin remains stable at 40.48 ℃. Both conditions satisfy the temperature control requirements of the equipment. Further verification is conducted through low-pressure environment simulation tests, showing that the maximum deviation between numerical calculation results and measured data is 7.9%. This confirms the reliability of the coupled radiation-convection heat dissipation analysis method. The simulation strategy considering surface solar radiation heat flux proposed in this paper provides theoretical support and engineering reference for the thermal management design of electronic equipment in extreme near space environments.