The invention discloses a beam up-tilt high-gain omnidirectional antenna, which comprises a first sub-array and a second sub-array which are coaxially arranged, wherein array elements are U-shaped symmetric oscillators. A dielectric substrate is provided with feeding lead wires for connecting the oscillators of the first sub-array and the second sub-array, the first sub-array and the second sub-array are connected with feeding cables by means of the feeding lead wires, the characteristic impedance of the feeding cable connected with the first sub-array is Z01, the characteristic impedance of the feeding cable connected with the second sub-array is Z02, the input impedance of the first sub-array Zin1 equals the characteristic impedance of the feeding cable connected with the same, the inputimpedance of the second sub-array Zin2 equals the characteristic impedance of the feeding cable connected with the same, that is, Z01=Zin1, Z02=Zin2, the first sub-array is an M-element sub-array, the second sub-array is an N-element sub-array, the M and the N are natural numbers greater than or equal to 1, and the M and the N are not equal. The beam up-tilt high-gain omnidirectional antenna disclosed by the invention has the advantages of having ultra wideband, high gain, high power, high efficiency and simple structure, and being horizontally omnidirectional, beam up-tilt, light and portable, and economical and durable.