The FBG being used as the basic sensor unit, a hydrophone sensor has been designed and manufactured. Its principle and relevant experimental result are introduced. By using the matched fiber grating demodulation technique, dynamic signal measurement with high sensitivity is realized. The frequency range of the FBG-based hydrophone is 10~3kHz with a dynamic range is 60dB. Due to the characters of FBG itself, the measure of multiple-points underwater signal can be realized conveniently by using WDM and TDM techniques.