Antenna array is one of the methods which can generate Orbital Angular Momentum (OAM) waves.However,OAM waves generated by different antenna arrays have different characteristics of Electric-field (E-field) components' distribution and radiation patterns.In order to solve this problem,we derive E-field formulas of OAM waves generated by different kinds of dipole antenna array in this paper.The dipole antenna arrays are arranged by three methods: 1) antenna elements are in the same direction ofy axis,2) antenna elements are in the radial direction and 3) antenna elements are in the azimuthal direction.Results show that x components,y components and z components carry different OAM modes under the three conditions.Simulation results show that the same direction antenna array produces the best OAM waves because they component is dominated by OAM mode l and RHCP/LHCP waves are negligible in energy,while the pure OAM waves carried by the z components generated by the other two antenna arrays have little energy.In addition,only the radiation pattern of l =0 produced by the same direction antenna array does not have a null zone in the propagation direction.Radiation patterns of l =±1 do not have null zones in the propagation direction generated by other two antenna arrays.