Abstract: The transfer matrix method is used to calculate the transmissivity of the defect mode of the photonic crystal with defects, and the influence of the absorption effect of material on the characteristics of photonic crystal temperature sensing is mainly discussed. The research object is the defect mode at the wavelength 800 nm. Simulated with the mathematical software MATLAB, it is found that: firstly, the transmissivity of the defect mode decreases with the increase of temperature, the photonic crystal is sensitive to the change of temperature; secondly, the absorption effect of material can slow down the speed of change of transmission peak with the change of temperature, and make the sensitivity of the photonic crystal changes less with temperature; finally, the greater the extinction coefficient of the material, the smaller the sensitivity of defect mode of the photonic crystal to the change of temperature.