The invention provides a high-gain wideband omnidirectional antenna, which comprises a main feeder, a two-cone shaped reflector, a wideband slot antenna, a feed network and an antenna cover. The high-gain wideband omnidirectional antenna has the characteristics of: 1, bandwidth of over 110 percent, higher radiation efficiency, adoption of inconsistent slot line shaped curves and contribution to further widening the bandwidth of the antenna; 2, capacity of being arranged in a plastic bucket and an antenna cover in any shape, ideal directional diagram, capacity of covering the whole space, uniform current distribution, capacities of realizing non-blind area coverage and improving communication quality; 3, capacity of compressing beam width in a vertical plane of the omnidirectional antenna so as to improve the antenna gain due to the adoption of the two-cone shaped reflector structure, capacity of making waves transmitted by a radiating unit radiate from the plane to free space, convenience for improving polarized purity of the antenna; 4, easy implementation of dual-polarized design; and 5, simple technology, fewer welding spots, convenient design and manufacture, and contribution to improving third-order passive intermodulation of the antenna.