The invention relates to the technical field of radar antennae, in particular to a low-profile C-waveband dual-polarization multi-layer microstrip patch antenna unit. A perpendicular polarization feed patch is adhered and fixed onto a reflective plate through an conductive adhesive; a first SMA type connector and a second SMA type connector are fixed to the reserves side of the reflective plate; an inner conductor of the first SMA type connector penetrates through the reflective plate, the perpendicular polarization feed patch, a cross recess type coupling slot patch, and a horizontal polarization feed patch to be connected with a metal wire on the upper surface of the horizontal polarization feed patch; an inner conductor of the second SMA type connector penetrates through the reflective plate and the perpendicular polarization feed patch to be connected with a metal wire on the upper surface of the perpendicular polarization feed patch. The antenna unit provided by the invention is small in size, light in weight, convenient in array plane integration, and higher in polarization isolation compared with a conventional dual-polarization antenna.