We report an electro-optic switch at 1.55 μm wavelength based on Mach-Zehnder Interferometer (MZI) in which, the MZI arms and the input-output 3-dB couplers are designed using plasmonic and photonic waveguides re- spectively. More than 90% photons are successfully converted into surface plasmons through tapering the both photonic as well as plasmonic waveguide. The plasmonic and photonic mode profiles, interaction between plas- monic and RF fields, confinement of plasmonic field in plasmonic waveguide, and trade-off between loss and confinement are thoroughly examined before the combined optical and electrical simulation of the switch. The switching voltage is less than 6 Volts, the MZI arm length is only 15 μm, the crosstalk is less than -35 dB, and the maximum switching speed is 11.55 ps. The footprint of the switch is only 290x50 μm2.