A tri-band aperture-shared antenna array is proposed for base-station applications. In the proposed aperture-shared antenna array, the antennas operating at high frequency-band (HB) and mid frequency-band (MB) are set beneath the low frequency-band (LB) antenna. To mitigate the interference raised by the LB antenna at MB and HB, one novel LB antenna with two transparent frequency bands is proposed, and therefore, good radiation performance is obtained at MB and HB although their aperture is overlapped with the LB antenna. Finally, one tri-band aperture shared antenna array is realized, the operating frequency band is 0.65-0.88GHz for LB, 1.92-2.18GHz for MB and 3.3-3.8GHz for HB, respectively. The proposed antenna array is verified through a prototype; good agreement can be observed.