Disclosed is an RFID system that includes a controller that outputs the transmission signal to be transmitted to an RFID tag and reads a receiving signal transmitted from the RFID tag; a leakage signal canceller that receives a portion of the transmission signal and the receiving signal, and performs an adjustment task to generate a cancellation signal according to an adjustment value and the portion of the transmission signal to remove a transmission leakage signal and to remove the transmission leakage signal included in the receiving signal; and a reader controller that determines whether there is a change of an RF environment using an intensity of the receiving signal according in a period set in advance, controls an operation of the leakage signal canceller according to the change of the RF environment, and controls an operation of the controller to read the receiving signal transmitted from the RFID tag.