A new demodulation method is proposed to eliminate the light intensity disturbance(LID) due to the Phase Generate Carrier( PGC) modulation method for the optical marine seismometer which is based on the fiber interferometer. A look up table by the use of a nonlinear function has been demonstrated. The experimental results show that the performance of the system has been improved with the harmonic suppression ratio(HSR) of the demodulation results increasing 30dB and the dynamic range of the system increasing 26dB, comparing with the Differential Cross-Multiplying(DCM) algorithm for the PGC method. The new method approaches a dynamic range of 130dB@100Hz with the HSR more than 50dB.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.