Abstract: In systematic operations, radars of different bands are often deployed in near area. In this case, the harmonic radiation of the low-band radar may interfere with other high-band radars. Therefore, it is necessary to consider the harmonic suppression ability of antenna when designing a radar, so as to improve the electromagnetic compatibility (EMC) of the whole combat system. In this paper, firstly, the transmitting link model of typical phased array antenna is established, and the source and propagation path of harmonics are analyzed. Then, the harmonic suppression is carried out from two paths: shielding isolation and link suppression. On the one hand, the three-stage shielding isolation is carried out through the packaging of power amplifier module, the shell of T/ R module and the all-metal closed high-frequency cabin. On the other hand, harmonic suppression targets are assigned to circulator, filter, radiating element antenna and array synthesis in the transmitting link, and the realization methods of harmonic suppression of each part are introduced respectively. Finally, the measured results of emission harmonics are introduced, and the harmonic suppression ability above -130 dBc is achieved.