A symmetric leaky wave antenna includes a dielectric substrate, an electric wall, and two reflection bore arrays. The dielectric substrate has a first and a second metal layers disposed on two opposite faces thereof. The first metal layer has a feed end and two travelling wave sides. The electric wall is disposed between two travelling wave sides, with the two travelling wave sides symmetrically disposed with respect to the electric wall. The two reflection bore arrays are symmetrically disposed along the two travelling wave sides, respectively, with the electric wall arranged at a central line between the two reflection bore arrays. The two reflection bore arrays pass through the first metal layer, the second metal layer, and the dielectric substrate. The reflection bore array and the electric wall reduce the leakage rate of the electromagnetic wave, thus increasing the gain value of the antenna.