In this paper, a surface acoustic wave (SAW) temperature sensor with a Pt/Ti/AlN/Mo/AlN/Si structure was prepared, and the high temperature characteristics of the sensors at 20–600 °C under different electrode metallization rates (ղ) were measured. It was found that frequent device mutation occurred in the first high-temperature test, and that the mutation point decreased with the increase in the electrode metallization rate (ղ). In the subsequent test, the data became stable, the sensor’s center frequency increased, the return loss (S11) decreased and the factor of merit (Q) increased. After annealing the same sensors at 600 °C for 30 min, they could achieve performance improvement in the first test, meaning that proper annealing can improve sensor performance. In addition, the annealed SAW sensor was tested in the temperature range of 20–1000 °C, which met the requirement of a temperature range of 20–900 °C, its f–T curve was linear, the factor of merit (Q) was 34.5 and the sensitivity was 46.6 KHz/K.