There is an error between the measured strain of the fiber Bragg grating sensor bonded on the surface of bending host material and the real strain of the host material. As a result, the issues of the deformation mechanism and the relationship between measured strain and real strain of the fiber Bragg grating sensor received considerable critical attention. First of all, the interaction mechanism between the fiber Bragg grating sensor and the host material was studied. Then, finite element solution, experimental value and theoretical solution were used for comparison and verification. Also, the causes of the errors were analyzed. Finally, the influence of the parameters (e.g., Young's modulus, thickness, bonding length) on the measurement effect of fiber Bragg grating sensor was studied. The results reveal that finite element solution, experimental value and theoretical solution exhibit the same variation trend. The error between finite element solution and theoretical solution is controlled within 2%, while the error between experimental value and theoretical solution is controlled within 7%. The average strain transfer rate increase with an increase of both the Young's modulus of the host material and the bonding length. Opposite conclusion held for the decreasing elastic modulus of the adhesive and increasing thickness of the adhesive. This theory has a certain guiding significance for the design of fiber Bragg grating sensors used for the strain measurement of the bending host material.