This paper proposes the design of weather radar antenna on X-Band frequency with two polarizations. The antenna is built based on slotted waveguide antenna array (SWAA) with its antenna structure consists of 2 layers, first layer is a radiating waveguide and second layer is a feeder waveguide. The first layer is composed of 5 waveguides in which each of waveguide consist of 64 slots, while the second layer is a single waveguide. The simulation result shows that the key antenna parameters performace reaches the specification such as: operating frequency = 9380 MHz, S11 = -22.567, bandwidth = 51.4 MHz, 3 dB-beamwidth for H-pol = 1.2 degree, 3 dB-beamwidth for V-pol = 1.0 degree, sidelobe level for H-pol = -17.3 dB, sidelobe level for V-pol = -15.2 dB, co-pol for H-pol = 20.6 dB, co-pol for V-pol = 16.2 dB, cross-pol for H-pol = -20 dB, and cross-pol for V-pol = -20.3 dB. Therefore, the proposed antenna is suitable for use as a weather radar antenna.