An array antenna, comprising a plurality of linear arrays ((1,5), (2,6), (3,7), (4,8)), a plurality of uplink-downlink duplexers, and a plurality of beam-forming networks, wherein, each of said linear arrays is a dual-polarized linear array consisting of a first antenna array (1, 2, 3, 4) having a first polarization direction and a second antenna array (5, 6, 7, 8) having a second polarization direction; wherein each of said uplink-downlink duplexers has one uplink signal output end, one downlink signal transmitting end and one shared transceiving end; each of said beam-forming networks consists of one input end and two output ends; the input end of each beam-forming network is coupled with a downlink signal output end of a respective radio frequency unit, and each output end of said beam-forming network is coupled with a downlink signal transmitting end of a respective uplink-downlink duplexer; downlink signal transmitting ends of said two uplink-downlink duplexers are only connected to said corresponding beam-forming network; shared transceiving ends of said two uplink-downlink duplexers are respectively coupled with arrays of two adjacent linear arrays having the same polarization direction and the two adjacent arrays having the same polarization direction form a beam with 65-degree beamwidth on a downlink through the said beam-forming network; uplink signal output ends of said two uplink-downlink duplexers are coupled with uplink signal input ends of said radio frequency unit; and arrays uncoupled with said uplink-downlink duplexers in the plurality of said linear arrays are all coupled with uplink signal input ends of said radio frequency unit respectively. each of said linear arrays is a dual-polarized linear array consisting of a first antenna array (1, 2, 3, 4) having a first polarization direction and a second antenna array (5, 6, 7, 8) having a second polarization direction; wherein each of said uplink-downlink duplexers has one uplink signal output end, one downlink signal transmitting end and one shared transceiving end; each of said beam-forming networks consists of one input end and two output ends; the input end of each beam-forming network is coupled with a downlink signal output end of a respective radio frequency unit, and each output end of said beam-forming network is coupled with a downlink signal transmitting end of a respective uplink-downlink duplexer; downlink signal transmitting ends of said two uplink-downlink duplexers are only connected to said corresponding beam-forming network; shared transceiving ends of said two uplink-downlink duplexers are respectively coupled with arrays of two adjacent linear arrays having the same polarization direction and the two adjacent arrays having the same polarization direction form a beam with 65-degree beamwidth on a downlink through the said beam-forming network; uplink signal output ends of said two uplink-downlink duplexers are coupled with uplink signal input ends of said radio frequency unit; and arrays uncoupled with said uplink-downlink duplexers in the plurality of said linear arrays are all coupled with uplink signal input ends of said radio frequency unit respectively.