A cavity-backed slot antenna is thought to be one of the most suitable elements for the wireless transmission of microwave energy. A design procedure for single fed low profile high performance X-band cavity backed slot antenna is described in this paper. The whole antenna including, backed cavity and, feeding element is completely constructed on a single substrate by using substrate integrated waveguide (SIW) technique. A single grounded coplanar waveguide (GCPW) is employed as the feeding element to excite the TE101 mode in the SIW cavity. An example is presented and the simulation results show 1% bandwidth, 5 dBi gain, 18 dB front-to-back ratio and 88.44 % radiation efficiency.