Aiming at the fatigue crack damage of typical aircraft and spacecraft metal structures, a fatigue crack monitoring and propagation prediction method for typical unilateral notched aluminum alloy specimens based on fiber Bragg grating (FBG) sensor is proposed in this paper. With the help of finite element simulation method, the strain distribution characteristics near the crack tip of fatigue crack with different length of unilateral notch specimens are obtained by numerical simulation, and the optimal layout of FBG sensors is given. Through fatigue loading test, the response characteristics of the center wavelength offset of FBG sensor with fatigue crack growth are obtained, and the prediction model of the relationship between the center wavelength offset and the crack length is established. According to the central wavelengthstrain response characteristics of FBG sensors at different locations, the fatigue crack region is identified. On this basis, according to the model of the relationship between the central wavelength offset and the crack length, the effective prediction of five different crack growth lengths is achieved with an average error of 1.6 mm. The results show that the proposed method has the advantages of nonvisual measurement and good realtime performance, and can provide a strong basis for health monitoring and residual life assessment of aerospace structures.