Design of a high power and high gain slotted waveguide antenna array operating in S-band has been presented. A standard rectangular waveguide WR-284 has been chosen for the slotted waveguide antenna and slots has been made on the narrow wall of the waveguide. A slotted waveguide antenna element with 36 pair of slots has been modeled and simulated using CST microwave studio. An array of 32 number of slotted waveguide antenna elements has been simulated and antenna gain in excess of 40dB could be obtained with 0.4º and 2º of horizontal and vertical beamwidth, respectively.