In this paper, a wireless monitoring system for graded Range of Motion (ROM) Arc device for shoulder rehabilitation using ultra high frequency (UHF) radio-frequency identification (RFID) at 920 MHz is proposed in order to realize self-service rehabilitation from 0 degree to 180 degrees; eliminating the manual monitoring. Using 11 passive UHF RFID tags, each tag is labeled and represents a 15-degree angle along the arc, the tag's Received Signal Strength Indicator (RSSI) variation from tag backscattering response could be used to determine the degree of the patient's shoulder movement mapping average 39 dB RSSI variation from -74 dBm (with full hand contact) to -35 dBm (without hand contact). An experimental prototype is built based on conventional ROM, patient's shoulder movement can be automatically recorded for further analysis by a therapist.