A dynamic-strain demodulating system based on a fiber Bragg grating (FBG) filtering is proposed and experimentally demonstrated.The FBG is glued onto the experimental laminate as smart material to monitor the structure vibration. Edge filtering of long-period fiber grating (LPFG) is used to demodulate FBG with light intensity. Throgh the connection of data collect card and LabView software, the voltage signal is transported to computer. Through the experiment, this system have a nice performance to reflect the exciting frequency. The vibration frequency up to 3 kHz can be realized and the wavelength resolving power is 0.004 nm in minimal.