The structure of a high-Tc superconducting power cable system is composed of these parts; (from the outer section) a liquid nitrogen cryostat, a vacuum cryostat, multi-layer high-Tc superconducting cable cores and a stabilizer and both cryostats during the stable operating period of the high-Tc superconducting power cable system are calculated by the numerical method. And the optimal conditions of the stabilizer and both cryostats, that minimize the eddy current losses, are derived from the analyzed results. The optimal results can be applied to the design and manufacture of the high-Tc superconducting power cable system.