Abstract: To improve accuracy of temperature measurement and system cost during cold chain transportation, a new UHF RFID tag IC with high precision temperature sensor is presented in this paper. A temperature sensor driven by PTAT current and constant current, which only calibrated by load capacitor array is adopted in this paper.Compared with traditional method, proposed circuits perform better on control simplicity, linearity, matching, and reliability. Improved demodulate block saves silicon up to 87% compared to traditional way. The IC is fabricated on TSMC 0.18 μm 1P6M CMOS process, in which total area and sensor area are 0.8 mm² and 0.05 mm² separately. Total power consumption is 14 μW. The temperature sensing accuracy is ±0.3℃ from 0℃to 50℃.