The adaptive carrier leakage canceler for UHF RFID reader adapts the cancellation of reflected power technology and an adaptive method similar to the steepest method and is used to cancel the leakage from TX to RX. The process is controlled by FPGA and the similar steepest decent method, which finishes the process in 100ms. The adaptive carrier leakage canceler exhibits more than 60 dB of carrier leakage cancellation over wide operating frequency band and the peak can reach 70dB.