A wrist worn RFID device with security protection includes a wrist worn body, a control circuit, a sensing circuit, a safety circuit, a RFID module and a processing circuit. When the control circuit detects that two connecting ends of the control circuit are electrically conducted due to two combined portions of the wrist worn body are fastened together, an enable signal is generated. The processing circuit controls the sensing circuit and the safety circuit according to the enable signal. When detecting the physiological signal, the sensing circuit generates a first validation signal. When the inputted user information is accepted by the identity verification program, the safety circuit generates a second validation signal. The processing circuit generates a control signal according to the first validation signal and the second validation signal, so that the RFID module implements a wireless transmission based on the control signal.