A ±45°dual-polarized base station antenna with a small size and a broad bandwidth for 2G/3G/4G/5G mobile communication is proposed in this paper. The proposed antenna comprises two pairs of dipole radiation patches, two microstrip feedlines and a reflector. The radiation patches and microstrip feedlines are printed on a FR4 substrate with a thickness of 0.8 mm, using a process called double-sided printed circuit board. The reflector is grooved a circular slot and the antenna is fixed above it. The prototype of the proposed antenna is fabricated and measured. The results show that it has a bandwidth of 1.82~3.60 GHz(port1) and 1.64~3.41 GHz(port2) respectively, during which, the reflection coefficient is less than -10 dB, the port isolation is better than 18 dB, the cross polarization discrimination is better than 17 dB in the boresight direction, and better than 15 dB in ±60°directions, the half power beam width is approximately 65°and the front-to-rear ratio is better than 18 dB. With the advantages of wide bandwidth, small size, simple manufacturing process and low cost, the proposed antenna is suitable for mass production and is an excellent candidate for applications in 5G mobile communication base station.