The fiber grating strain sensor is developed by using the 3D-printing method. A separate model of strain coupling and transmission between the bare fiber Bragg grating sensor， 3D-printing encapsulation layer and the measured matrix structure is established. The strain transfer relationship between the fiber grating sensor and the measured matrix structure is deduced. The influencing factors of the strain transfer rate of the clamped 3D-printing fiber grating strain sensor are analyzed， including the elastic modulus of the encapsulation layer， the thickness of the encapsulation layer and the bonding length. The research results show that the average strain transfer rate is positively correlated with the elastic modulus and bonding length of the encapsulation layer， negatively correlated with the thickness of the encapsulation layer. The research results can be used as a reference for the clamped fiber Bragg grating strain measurement， error correction and sensor design， as well as the feasibility of 3D-printing technology for packaging fiber Bragg gratings.