The invention discloses a miniaturized flexible fiber bragg grating strain sensor. The miniaturized flexible fiber bragg grating strain sensor comprises an optical fiber, a fiber bragg grating, a high-elasticity modulus polymer material coating layer, a low-elasticity modulus polymer material coating layer and a high-elasticity modulus polymer material interlayer. Part of the optical fiber is burnt with the fiber bragg grating, and the surface of cladding of the optical fiber is coated with the high-elasticity modulus polymer material coating layer; the position, corresponding to the part, burnt with the fiber bragg grating, in the optical fiber, of the surface of the high-elasticity modulus polymer material coating layer is coated with the low-elasticity modulus polymer material coating layer. The part, coated with the low-elasticity modulus polymer material coating layer, of the optical fiber and the parts, on the two sides of the fiber bragg grating, of the optical fiber are fixed into the high-elasticity modulus polymer material interlayer. The miniaturized flexible fiber bragg grating strain sensor is suitable for strain testing of the surfaces and interiors of composites andmetal structures in multiple shapes, the strain transmission efficiency is high, and the reflection spectrum of the fiber bragg grating is not likely to chirp.