Coils and iron cores are the key components of a saturated iron core superconducting fault current limiter (SI-SFCL). They determine the entire performance of SI-SFCLs under both operation modes of fault current limiting and normal power transmission. Besides, they have great impact on scale, weight, and manufacture cost, which are essential factors in developing functional and cost-effective SI-SFCLs. We have intensively investigated the correlation between the design parameters of coils and iron cores and their influence on SI-SFCL characteristics. Theoretical analysis and experimental measurements have been carried out and parameters of nonlinear calculation from theoretical analysis are derived from the results of experiments. A 500-V SI-SFCL was developed and a selection of experiments were designed and completed to prove that an optimized design exists under certain current limiting and voltage drop conditions. Details of methods and results will be presented and discussed in this paper.