The optical characteristics of the magnetic metamaterial (MM) composed of the ferrite rods are theoretically investigated. Firstly, a photonic band-gap (PBG) resulting from the magnetic surface plasmon (MSP) resonance is recognized by observing the photonic band structure. Moreover, the PBG can be manipulated flexibly by using an external magnetic field (EMF). In particular, the effect is very roust against structural perturbations, which can be corroborated by examining the transmittances for a MM slab with different position disorders and size fluctuations. Based on this peculiar property, we design an electromagnetic switch with fast response, which is demonstrated by calculating the electric field patterns of a Gaussian beam incident on a MM slab.