Radio　frequency　identification　(RFID)　tags　are　widely　used　in　various　electronic　devices　due　to　their　low　cost,　simple　structure,　and　convenient　data　reading.　This　topic　aims　to　study　the　key　technologies　of　ultra-high　frequency　(UHF)　RFID　tags　and　high-precision　temperature　sensors,　and　how　to　reduce　the　power　consumption　of　the　temperature　sensor　and　the　overall　circuits　while　maintaining　minimal　loss　of　performance.　Combined　with　the　biomedicine,　an　innovative　high-precision　human　UHF　RFID　chip　for　body　temperature　monitoring　is　designed.　In　this　study,　a　ring　oscillator　whose　output　frequency　is　linearly　related　to　temperature　is　designed　and　proposed　as　a　temperature-sensing　circuit　by　innovatively　combining　auxiliary　calibration　technology.　Then,　a　binary　counter　is　used　to　count　the　pulses,　and　the　temperature　is　ultimately　calculated.　This　topic　designed　a　relaxation　oscillator　independent　of　voltage　and　current.　The　various　types　of　resistors　were　used　to　offset　the　temperature　deviation.　A　current　mirror　array　calibration　circuit　is　used　to　calibrate　the　process　corner　deviation　of　the　clock　circuit　with　a　self-calibration　algorithm.　This　study　mainly　contributes　to　reducing　power　consumption　and　improving　accuracy.　The　total　power　consumption　of　the　RF/analog　front-end　and　temperature　sensor　is　$7.65\mu　\text{W}$.　The　measurement　error　of　the　temperature　sensor　in　the　range　of　0　to　60°C　is　less　than　±0.1%,　and　the　accuracy　of　the　output　frequency　of　the　clock　circuit　is　±2.5%.　©　2013　IEEE.