Abstract: In thermal vacuum tests, the maximum irradiated area of the solar simulator is fixed. In order to meet the demand for an increased radiation range, a combined heat flux simulation approach is proposed, which combines the simulation of the absorption heat flux and the incident heat flux. A scheme of using the infrared lamp array together with the solar simulator could effectively ease the requirement of a large spot diameter with regard to the solar simulator system, thus reduce the cost of the test. The influence of the heat flux interference and overlapping is analyzed, and on that basis, a light shield is introduced to provide a more adequate heat flux. The ground tests are carried out and the temperature data analysis indicates the adequace of the simulation method and the reliability of the test data.