The performance of an AlN/sapphire temperature sensor operated at high temperature is investigated. To optimize the output performance, several different structural surface acoustic wave devices are fabricated, including one-port resonator and delay lines with various gaps. The effects of the electromechanical coupling coefficient (), insertion loss, and temperature coefficient of frequency on temperatures are demonstrated in detail. increases with the increasing of the temperature and the insertion loss increases at the beginning, but decreases at higher temperatures due to the influence of the rising . The frequency responses of both the resonator and delay lines show very good linearity with temperature and both of them exhibit excellent stability.