An ultra-compact dual-polarized cross-dipole antenna with a small projected area is proposed for Sub-6 GHz base stations, which includes radiating layer, defected ground layer, metal mesh reflector, coaxial lines, and plastic posts. The radiating layer is composed of two vertical bow-tie dipoles, which are respectively excited using two coaxial lines. The defected ground structure is utilized on the ground layer to dramatically reduce the projected area while keeping radiation performance. To reduce wind loading, the traditional metal reflector is replaced by a metal mesh reflector. The proposed antenna shows a very compact structure, small projected area, and high performance, which has great potential for ultra-massive MIMO system operating at the Sub-6 GHz band.