The interrogation system based on a Fiber Bragg Grating sensor was designed for damage identification by using a unbalanced M-Z interferometer and a Phase-Generated-Carrier (PGC) technology according to the features of vibration type Structural Health Monitoring (SHM) method. The damage indicator

namely the sum of relative variation ratio

was constructed based on the wavelet packet node energy of vibration signals. Then

the control principle of statistical process was introduced and the index of damage identification was derived by using X-R statistical process control. The 160 vibration signals of an aluminum simply supported beam under a health state and three kinds of damage states were measured using FBG interrogation

and results show that the duration of time domain vibration signal in each state is approximately 0.05 ms and their amplitudes are basically the same. The damage identification was analyzed based on the statistical process control limit (12.85

41.35)

and it is concluded that the damage identification system is good at continuously structural health monitoring.