Abstract: Optic fiber Bragg grating sensor requires a strain transfer coefficient when it is embedded in or adhered to the structure due to an interlayer between structure and sensor. The important factors that affect the strain transferring are deduced on the basis of existent theory in this paper, which include the length of the sensor, the thickness, Young’s modulus and Poisson’s ratio of the interlayer. The relationship between the average strain transfer rate and the parameters is discussed. The results show that the average strain transfer rate increases with sensor length, decreases with the thickening of the interlayer, rises with the increase of the interlayer Young’s modulus. The influence of the interlayer Poisson ratio on the average strain transfer rate is very small and it can be neglected when choosing the interlayer parameters.