The current state of the disk angular position information is obtained by using high-density optical encoder, and the output signal is demodulated by using the angular position information as initial phase angle of gravity gradient demodulation reference signal, then the arithmetic mean of the each demodulation result of gravity gradient information is calculated, and the two groups of gravity gradient information are subjected to smoothed filtering processing respectively. Finally, the gravity gradient demodulation is tested on the Hardware-in-the-Loop simulation platform. The experiment results demonstrate that the gravity gradient signal accuracy is further improved, and the method has such good properties as high practical applicability and maneuverability.