A method of upgrading an operation program in an interrogator of a radio frequency identification (RFID) system including the interrogator and a transponder is provided. The method includes transmitting, from the interrogator to the transponder, a first message requesting an operation program upgrade based on information exchanged between the interrogator and the transponder; receiving, at the interrogator from the transponder, a second message that includes a new-version operation program in response to the first message; and installing, at the interrogator, the new-version operation program to upgrade the operation program in the interrogator.