The invention provides a phased array seeker antenna, which comprises more than 300 phased array antenna units with an even number, wherein the working state of each antenna unit comprises a seeker mode and a fuse mode; the antenna units simultaneously work in the seeker mode; one part of antenna units work as transmitting antennas, one part of antenna units work as receiving antennas and the other part of antenna units are closed and do not work in the fuse mode; the types of the antenna units are uniquely determined by antenna technology indicators in the seeker mode; the number of the antenna units is uniquely determined by transmitting power indicators in the seeker mode; and the distribution structure of the antenna units is uniquely determined by a common-calibre detection system structure. According to the phased array seeker antenna, the detection requirements of seeker and fuse two different working modes on a target are achieved through time sharing of a same planar phased array antenna; a common-calibre antenna design of the seeker/fuse is really achieved; the phased array antenna is flexible, controllable and fast in beam switching; and the expandability of a system is strengthened.