The existence of large air gaps, between a high-Tc superconducting (HTS) tube and an iron core, or between a primary winding and a HTS tube, possibly causes some undesirable voltage drops ender the condition of normal operation. It makes the power system unstable. For this reason, the optimization of air gaps is essential in designing a high-Tc superconducting fault current limiter (SFCL), In this paper, the optimal values of air gaps are determined through electromagnetic analysis, and the comparison between computational and experimental results is provided.