Saturated iron-core type superconducting fault current limiter(SICS-FCL) has non-linear impedance characteristics. The electromagnetic transient process after connecting to 500 kV power grid has an important impact on the safe and stable operation of power grid. According to the single-phase three-column core structure of the 500 kV SICS-FCL, the coupling relationship between the main electromagnetic parameters is analyzed by magnetic circuit decomposition method. The complex magnetic circuit analysis model is transformed into equivalent circuit model. The electromagnetic transient simulation model is built on the PSCAD/EMTDC simulation platform. Finally, combined with the parameters of 500 kV power grid and the design scheme of SICS-FCL prototype, the transient impedance characteristics under steady-state operation and different short-circuit faults are analyzed through specific examples. The results are consistent with the theoretical analysis.