The Two-Phase Fluid Loop (TPFL) System is a heat transport system for future large spacecraft, using latent heat of coolant. TOSHIBA Co. has developed a ground test facility capable of dissipating a 5kw heat load and tested the components of that facility since 1988. As a next phase, static characteristics of the TPFL system are being studied.In this paper, static behaviors under heat load variation are presented as results of the experimental study and the numerical simulation. For the experimental study, the above-mentioned ground test facility was used. In this facility, heat is finally dissipated to the heat exchanger using brine as a heat sink. In order to determine static behaviors for an actual radiator heat rejection system used in orbit, numerical simulation was carried out.To confirm the analytical model used in the numerical simulation, the numerical result and the experimental result were compared.