A tilted bi-sense circularly polarized (CP) antenna and its application for UHF radio frequency identification (RFID) system is proposed. A planar concial monopole working as the electric dipole is designed at first. When a shorting pin is added, a loop radiator would be generated, and thus a pair of orthogonally oriented complementary dipoles is realized. In this way, both right-handed circularly polarized (RHCP) and left-handed circularly polarized waves (LHCP) are generated simultaneously in tilted directions within one hemisphere. Then, closed-form formulas are derived to reveal the tunability mechanism of bi-sense property and provide a design guideline for system application. It is demonstrated that flare angle of conical monopole has a linear relationship and sine function to CP beam direction and 3-dB axial ratio (AR) beamwidth, respectively. Finally, antenna prototypes are fabricated and tested for validation. It is also demonstrated that at the tilted direction of θ = ± 45°, a 3-dB AR bandwidth of 4.9%, and gain up to 5 dB are realized. Comparing with conventional microstrip patch antenna, an enhanced reading range over 5 m can be obtained in the tilted range from 40° to 75° and − 75° to −40° in UHF RFID sytem application.