The temperature characteristics of the Rayleigh wave mode resonant frequency and the bulk acoustic wave mode resonant frequency of SAW resonators based on La3Ga5SiO14 (LGS) piezoelectric substrate were studied in this work. Based on these two modes, a dualmode temperature sensor with wide temperature range and linear output characteristic was proposed. The results show that the resonance frequencies of both the Rayleigh wave mode and the bulk wave mode of the LGS resonator are a quadratic function of temperature. And the secondorder frequency temperature coefficients of these two resonance modes are nearly equal. The temperature measured by the proposed dualmode temperature sensor is the same as that measured by the thermocouple. The dualmode temperature sensor proposed in this work has linear output characteristic in the whole temperature range and can be used in the high temperature SAW temperature sensor based on LGS.