The polyimide coatings with different thickness were deposited on the surface of surface acoustic wave (SAW) resonator based on LGS substrate. The effect of the polyimide coating on the characteristics of the SAW resonator was investigated. The results indicated that the resonance frequency of the SAW resonator decreased when the resonator is coated with polyimide film. As the thickness of the polyimide layer increased, the resonant frequency of the resonator decreased more. The absolute value of the firstorder frequency temperature coefficient of the SAW resonator increased and the turnover temperature shifted to lower temperature with the increase of the thickness of polyimide film. The results present that the polyimide coatings can improve the temperature sensitivity of the LGS SAW resonator, which can be applied to temperature sensors.