An optical fiber refractive index sensor based on D type multi-film f iber surface-deposited alternating grating is presented.The transmission spectrum and the mechanism of the Resonan ce Absorption Peak of the Sensor are studied by using the transfer matrix method and the finite-difference time -domain method FDTD method.Based on the difference sensitivity of the refractive index and temperature of the two resonant modes,the wavelength of the two peaks is chosen as the information carrier,the sensitivity and quality fact or of temperature compensated refractive index sensor are 562.8nm/RIU and 24.14/RIU,respectively.The sensor has the ad vantages of simple structure,small volume,and easy integration,eliminating cross-sensitive interference of tempe rature and being more practical.