A dynamic demodulation method of fiber Bragg grating (FBG) vibration sensor based on cascaded long-period fiber grating (CLPG) is proposed. The light of broad optical source is reflected by FBG, then the reflected light entrances the CLPG. The intensity of reflected light of FBG changes after being modulated by CLPG. Monitoring system is calibrated by temperature-measuring experiment firstly. Then FBG is stuck on the surface of aluminum specimen, and wavelength change of FBG caused by vibration of the aluminum specimen in low and high frequence is monitored by the system. The acquired vibration signal and fast Fourier transform (FFT) of the experiment data agree with the signal of eddy current displacement meter. It is shown that the FBG dynamic demodulation based on CLPG can be used to monitor no more than 2 kHz dynamic signal.