For solving noise disturbance in marine gravity anomaly measurement and improving accuracy of measurement, FIR low-pass filter technology is applied to high-frequency noise ingredient included in gravity anomaly measurement and the real gravity signal can be recovered. This paper mainly presents the principle and method for designing digital low-pass filter. By applying Discrete Fourier Transform (DFT), different frequency components of both original gravity signal and noise signal are discriminated from this measurement. On the basis of frequency spectrum analysis of gravity measurement, frequency sampling technique is adopted to design low-pass filter and it can well match the gravity measurement signal characteristics. Finally, this method is carried out with previous experimental data. The results demonstrate that the filter designed by frequent sampling method can effectively remove high-frequency noise and the standard error can be within 1mGal.