Abstract: The characteristics of Fabry-Perot(F-P) etalon can be easily affected by temperature, the transmission peaks of F-P etalon drift with the fluctuation of temperature, and when F-P etalon is applied in the fiber Bragg grating(FBG) wavelength demodulation, the fluctuation of temperature may cause wavelength demodulation error. The impact of F-P etalon temperature characteristics on the FBG wavelength demodulation accuracy was analyzed, and the stability experiment and repeatability experiment were carried out using F-P etalons with thermal stabilities of 1.5 GHz and 3 GHz respectively. The analysis and experimental results show that the standard deviation of the demodulation error which is generated by the temperature characteristics of the F-P etalon is different if the center wavelength of the FBG sensor is different; the maximum stability errors obtained by two F-P etalons are 0.528 pm and 0.676 pm, and the maximum repeatability errors are 1.77 pm and 2.01 pm respectively.