Ion cyclotron resonance heating is a reliable tool for high-power and long-pulse operation in fusion reactors. However, a sudden increase in the reflected radio-frequency (RF) power poses serious problems such as L- to H-mode transition or edge-localized modes that must be solved for future fusion reactors. It is necessary to place an impedance matching system between the RF generator and antenna to mitigate the adverse effects of the variations. The idea of a fast-response ferrite stub tuner was developed to trace the load variation of the antenna. This study presents theoretical calculation of the suitable normalized mechanical length of the ferrite stub tuner using transmission line theory and numerically analyzes the impedance matching parameters of the single ferrite stub antenna system. The present study demonstrates the feasible investigation of the magnetic field modulation, which can lead to the effective reduction in the reflected RF power fraction during the large change in plasma resistance.