Abstract: Loop heat pipe with flat evaporator (Flat Loop Heat Pipe, FLHP) driven by capillary force and mechanical pumped two-phase loop (Tracker Thermal Control System, TTCS) are typical two-phase loop thermal control systems. The working principles of both FLHP and TTCS are discussed in this paper, and samples are tested. Also, dynamic models are built by both SINDA/FLUINT and Matlab/Simulink. The results show that both the FLHP and TTCS may have start-up problem, that the FLHP may have larger temperature oscillation, while the TTCS are more stable, that gravity has obvious effect on the FLHP performance, yet has no obvious effect on the TTCS performance, and that the FLHP with bi-transport loops has a better performance than that with single-transport loop, and the two radiators of the TTCS has the ability of self-adjust in mass flow rate and heat transfer. To choose a two-phase thermal control system, some items should be considered, such as the characteristic of the heat source, the life requirement, the temperature requirement, as well as the system size and mass, etc. Development of the two techniques may be cross-reference and complementary in future.