In this letter, a magnetically controlled surface-loaded ferrite single pole single through (SPST) switch is presented. The ferrite slab is loaded on the broad wall surface of a substrate integrated waveguide (SIW). When a dc magnetic bias is applied to the ferrite slabs, the effective permeability of the ferrite becomes negative. In this case, the wave will be cut off. After investigating the design principle, an X-band switch prototype is fabricated and measured. Its insertion loss is less than 1.6 dB, return loss is better than 15 dB, and isolation is better than 27 dB in a frequency range from 9.5 to 11 GHz.