High integration, miniaturization and high-power of electronic components are developed in space flying-vehicle at expense of increasing heat dissipation. Therefore, the advanced thermal management technology is becoming a major factor to restrict the safe and efficient flight of future aircraft. According to the special space environment characteristics, work pattern and requirement of thermal control of high-power control units using in near space flying-vehicle, a thermal management system is designed by means of cold plate technology, thermal control coating, decreasing thermal resistance, and improving heat-exchanging efficiency etc. The optimal design scheme is presented by means of ANSYS simulation. In view of the requirements of the object and temperature design, three kinds of structures are designed. And numerical results point out that the design scheme of increasing the edge area of cold plate and the surface area of radiation heat dissipation and natural convection heat transfer is the best choice to control the temperature at the range of 293.15-318.15 K for efficient and reliable work.