Abstract: The temperature of thermal management system in hypothetic space lab is illustrated. The model of the system is consisted of external and internal thermal control sub-system, avionics air cooling sub-system in racks, cabin air cooling system and two sub-modules of heat transfer. The one of sub-modules modeled heat transfer by radiation and conduction among equipment, racks, gas cylinders and inner cabin wall. The other modeled heat transfer by radiation among outer cabin wall, radiatior, solar panel and external radiation environment. The results of temperature's modeling of the system will not only support design of thermal management system of large spacecraft, but also provide system analysis, which included sensible analysis, test data correlation, optimizing design, reliability analysis and robust design. The thermal management system can be extended to energy system by adding power sub-system and then the modeling of thermal system will benefit to analyse energy balance and power/thermal system matching of the energy system.