Abstract: A novel structure of a capacitive Micro-Electrical-Mechanical-System （MEMS） RF switch was presented. A part of CPW transmission line is made up of Metal/Dielectric layers whichis above a cavity on a silicon wafer with a resistivity of 4-8 Ω·cm, it can move up and down acting as a RF switch. The RF switch with dimension of 1000μm×600μm×300μm was fabricated by thesurface micromachining technology. In the range of 50 MHz to 10 GHz, the switch actuates under 35 V,the insertion loss and isolation are measured to be less than 2dB and better than 40dB, respectively.