Abstract: In this paper, an omnidirectional antenna with a low profile and high horizontal gain based on near-zero refractive index metamaterial（NZRIM） is designed. The metamaterial cell consists of two symmetrical C-shaped strips and a curved line strip. The array composed of metamaterial elements is symmetrically placed around the omnidirectional antenna. The radiation direction of the electromagnetic wave is changed effectively approaching the horizontal plane. Thereby the horizontal gain of the antenna is improved. The measured results show that the-10 dB impedance bandwidth of the antenna is 5.78 GHz～6.12 GHz. By loading the NZRIM, the horizontal gain of the antenna increases by 0.5 dB～1 dB in the working bandwidth, with its maximum reaching 2.68 dBi.