In this paper, a new broadband omni-directional antenna which utilizes dual-parasitic sleeve structures with a metal pole through the radiator for VHF/UHF operation is designed. The radiator includes biconical-structure and thick dipole in order to reducing the size. This antenna can combine satellite navigation antenna to form a new mast antenna by use of this structure to improve the impedance. The working frequency band of the antenna is 120-550MHz. In the whole band the VSWR is less than 2.5. The measured and simulated results show that the antenna has good omni-directional pattern properties over high and low frequency