Abstract: In view of the requirement for high precision heat flow simulation for different components on a remote sensing satellite, a combined heat flow simulation approach was proposed. Infrared heating cages were used to simulate the external heat flow on the surfaces of satellite cabin panels, while thin film electric heaters were utilized to simulate the external heat flow on complex surfaces of satellite. With the satellites’ status and the thermal design measures taken in the test, the proposed method may be able to accurately simulate the external heat flow of the satellite under working conditions of low-temperature initial period, high-temperature final period, and high temperature thermal vacuum test, in addition to effectively assess the thermal control design of remote sensing satellites. It may also provide a reference for the optimization of transient power dissipation design of satellites, and offer technical support for the thermal balance test and verification of China’s future optical remote sensing satellites.