The “environment-drifting” coused by the enviromental factors will happen to the work point of an interferometric fiber optic sensors. In the phase generation carrier (PGC) digital demodulation process,when the drifting gets through the integral link,it increases with the growth of time;the large enough drifting will lead to register′s overflowing and the reset of the digital demodulation system,and the last part of the signals of the demodulation result will be hiden. Focusing on the integral effects and using the low-frequency characteristic,a method of low-pass filtering (LPF) elimination is put forward,and the relevant solution is given. The experiment result shows that the method settles the integral effects of environment drifting well.