Abstract: In order to satisfy the application requirements of multifunction and integration, the phased array antenna is developing towards ultra-wideband, miniaturization and lightweight. Based on the tightly coupled technology, a low-profile ultra-wideband tightly coupled phased array antenna is designed. The antenna unit consists of a metasurface wide-angle matching layer, a radiation dipole, a Marchand balun and a metal floor. The tightly coupled effect is realized by overlapping the upper and lower layers of the dipole arms. Through simulation, the active standing wave of the tightly coupled antenna is less than 3. 2 at 0° ~ 50° scanning angle in the 1. 4 GHz ~ 6 GHz band, which has a good impedance matching bandwidth. Finally, the 18× 36 array antenna is tested, which verifies that the measured results are consistent with the simulation results.