In the multi-application of the Internet of Things (IoT), it is necessary to realize the identification and sensing functions simultaneously, which is one of the advantages of surface acoustic wave (SAW) technology. A SAW tag with encoding capacity of nearly 3 million is designed by using the scheme of combining the pulse time delay and phase encoding, and the principle of integrated identification and temperature measurement is analyzed. In order to improve the accuracy and stability of identification and temperature measurement, a digital orthogonal demodulation scheme based on radio frequency direct undersampling is used to design the corresponding reader.A miniaturized folded dipole antenna is designed and fabricated on the flexible circuit board, which expands the application field. The actual test results show that the builtup system can work normally in the temperature range of -20~60 ℃, and can not only realize accurate identification within 2 m, but also reach the temperature measurement precision of 0.6 ℃.