This paper proposes a new low profile dual band WLAN planar inverted-F antenna (PIFA) by using electromagnetic band-gap (EBG) material as ground plane. The total thickness of this antenna is only 4 mm, which is half of the height when a normal perfect electric conductor (PEC) ground plane is used. The backward radiation ratio is also reduced as the existence of EBG. Moreover, the bandwidth for the 5 GHz band is increased by 10 times compared to the reference antenna. This EBG PIFA is built on the ground plane with size of 40times62 mm, which is suitable for most of the mobile devices.