With the continuous progress and development of science and technology, more and more new composite materials were used in the industrial manufacturing process. Because the damage of composite materials during service will lead to huge losses, it is very important for structural health monitoring of composite materials. Fiber Bragg grating (FBG) sensor technology was used in the detection of glass fiber composite sheet. Glass fiber composite was incented using active impact way, and impulse response signal before and after the injury was collected. Based on the wavelet packet energy spectrum, the impact response of the damage identification was realized by wavelet packet decomposition, and the histogram of wavelet energy spectrum changes ratio before and after the injury was obtained. By comparing each order wavelet packet energy ratio, the damage identification of the glass fiber composite was realized.