Based on an array of dipole antennas, an antenna with the characteristics of horizontal omnidirectional radiation pattern, horizontal polarization and planar structure is proposed. The antenna is composed of three dipole antennas, whose radiators are bent 30° and printed on a PCB(Printed Circuit Board) in an alternative way(top and bottom), and forms a hexagon ring with a diameter of 0.45λ0(λ0 is the free-space wavelength). The three dipole antennas are directly fed through SMA(Small A Type) connectors, and thereby feeding baluns can be cut. By optimizing the structural parameters such as the dipole antenna’s length and distance, as well as controlling the feeding phase, a horizontal and omnidirectional radiation pattern is realized. As a sample, such an antenna working at the frequency of 2.45 GHz is designed, fabricated and tested. The measured results agree well with the simulated ones, indicating the antenna has encouraging features such as the impedance bandwidth of 12.94%(2.367-2.684 GHz) with |S11|≤10 dB, and a good horizontal omnidirectional radiation pattern with the gain of 1.42 dBi and gain variations within ±0.7 dB.