Concurrent data communication based on backscat-ter is an unnoticed research domain in the past, but recently it is considered as a promising technology for Massive IoT in the B5G/6G wireless sensor network (WSN). In this domain, it is a practical multiple access solution to use multiple subcarriers. This paper proposes a frequency continuous calibration method to improve the frequency accuracy of uplink subcarrier (USC) in the concurrent data communication mode, called USC continuous calibration (USCoCa). Tag obtains a 10kHz amplitude modulation frequency reference from reader, uses a digital frequency lock loop to calibrate the on-chip digital controlled ring oscillator, and generates USC with a wide frequency range and good frequency accuracy. The tag with USCoCa is fabricated with 0.51×1.02 mm 2 area size. The test result shows that US CoCa can keep continuous calibration of USC frequency, and the USC frequency deviation is less than 0.25 % within the range of 100-620kHz frequency. At the same time, the USC frequency stability can even be maintained under the +134°C /min rate temperature environment. Therefore, USCoCa can ensure stable frequency channel assignment for the multiple sub carrier UHF RFID system and guarantee robust concurrent data stream transmission.