The invention relates to an X-band satellite-borne phased-array antenna. The X-band satellite-borne phased-array antenna comprises an antenna cover, an installation plate and a plurality of same antenna units, wherein centers of the plurality of antenna units are arranged on the installation plate in an equilateral triangle lattice mode, the antenna cover covers the plurality of same antenna unitsand is fixed with the installation plate, each antenna unit is a multi-layer microstrip antenna and comprises a radiation patch, an antenna unit shell, an SMA coaxial connector, a grounding plate, abottom-layer dielectric plate, an upper-layer dielectric plate and a parasitic patch, an inner core of the SMA coaxial connector sequentially penetrates through the installation plate, the grounding plate and the bottom-layer dielectric layer and is connected with the radiation patch, an outer skin of the SMA coaxial connector is fixedly connected with the installation plate, the installation plate is connected with the grounding plate, the radiation patch is arranged on the center of the bottom-layer dielectric plate, the parasitic patch is arranged in the center of an upper surface of the upper-layer dielectric plate, an air medium is arranged between the bottom-layer dielectric plate and the upper-layer dielectric plate, and the peripheries of the bottom-layer dielectric plate, the grounding plate and the upper-layer dielectric plate are fixed with the antenna unit shell.