In order to achieve automatic monitor the seepage of dam,a monitoring structure with fiber Bragg grating sensors using spectral imaging technique and the multi-point sensing network system is proposed.The fiber grating sensor system structure with linear InGaAs array and diffraction grating is designed.With the analysis results from laboratory of precision and reliability in seepage monitoring,the 0.009 1 nm/℃ wavelength-temperature response sensitivity of the Fiber Bragg Grating sensors used for temperature field monitoring of dam is presented.By analyzing the signal resolution factor of the multi-point sensor,the multiple sensors multiplexing of the testing system determined by dominated optical source bandwidth are researched.By using multiple fiber Bragg grating temperature sensors embedded into dam,the multi-point measurement of temperature differences is achieved to realize seepage monitoring of dam.Engineering practice shows that the system of seepage monitoring of dam has good performance in resistance to thunderbolts and disturbances as compared with conventional instruments.