In this paper,based on the oppositely directed currents(ODCs),a near field Radio Frequency Identification (RFID)reader antenna at ultra-high frequency(UHF)band is introduced. How structure parameters of antenna affects current distribution along the two elements are studied further. Once the length of the excited element and the operating frequency is given,the phase difference of currents along the two elements is determined by the length of parasitic element and the pitch between the two elements.To realize the ODCs,the length of the parasitic element and the distance between two elements should satisfy a corresponding relationship. With different requirements of the magnetic field distri-bution and the recognization areas,the length of the parasitic element with corresponding distance between two elements can be chosen flexibly. When the distance between the two elements is small,the length of parasitic element close to λ/2 is suitable. While when the distance is large,the length of parasitic element can be chosen among a large range. Finally, two examples are given to prove that the method introduced in this paper is reasonable.