A waveguide slot array antenna used for satellite communication consists of three waveguide layers, the first layer is a radiating layer, the second layer is a coupling layer or a feeding layer, and the third layer is a feeding layer, the three layers are directly welded / connected sequentially, each layer consists of two waveguides with different specifications, and the two different waveguides respectively generate two radiation slots with different sizes on the antenna radiating layer to produce two different receiving frequency and emission frequency; in the two different radiation slots with different sizes, one slot is in the direction of the waveguide length, and the other slot is in the direction of the waveguide width, the two slots are mutually orthogonal; the radiating waveguides of the two mutually orthogonal slots with different sizes are alternately and closely arranged side by side and generate orthogonal polarization properties which are perpendicular to each other to meet the special requirements of satellite communication while sharing an antenna aperture face. The invention provides a satellite communication antenna which can be satisfactorily applied to transmitting and receiving satellite signals and is characterized by small occupation space, wider use frequency of antenna and lower feeding loss, and the structure of the antenna is reduced from three layers to two layers to cause the antenna to be more easily processed. The antenna is particularly suitable for the occasions such as narrow airborne, vehicle-borne spaces, etc.