A novel dual planar electromagnetic bandgap (DP-EBG) microstrip structure with wide stopband and flat passband is presented. It is demonstrated that the proposed structure achieves a Ultra-Wide stopband and excellent passband performance within a compact circuit area. And the DP-EBG structure is employed in the feed line of patch antenna with the aim of suppressing harmonics and other spurious modes. Simulated and measured results indicate that the application of this DP-EBG structure not only drastically diminishes spurious radiations of 2nd ∼ 6th harmonics in a broad frequency band, but also overcome some shortages of other EBG microstrip antennas introduced in previous research.