This paper explores the effect of an air-gap between a ferrite plate and metal strips on magnetic shielding in the presence of a periodic line current source based on an analytical solution. The Fourier transform is used to represent the magnetic vector potentials in the spectral domain, and the mode-matching technique is enforced to obtain a modal solution in rapidly converging series form, leading to numerically efficient results. Magnetic shielding effectiveness is investigated in terms of the air-gap thickness between the ferrite plate and metal strips, the metal strip width, and the position of a periodic line current source.