The invention provides a complementary filtering-based underwater glider energy saving method. The method comprises the steps of acquiring velocity information of an underwater glider in real time by using a Doppler log; judging the motion state of the underwater glider according to the velocity information; when the underwater glider is in a high dynamic state, starting an accelerometer and a gyroscope, and fusing information of a magnetometer and information of an inertial measurement unit (IMU) by means of complementary filtering so as to improve navigation accuracy; if not, stopping the accelerometer and the gyroscope, and completing navigation only by using the Doppler log and the magnetometer. The method prolongs the working time of the underwater glider and improves the endurance of the underwater glider by selectively starting and stopping the IMU; furthermore, an innovative complementary filtering information fusion algorithm is adopted, so that the working accuracy of a glider navigation system is improved, and the accuracy of the navigation without IMU calculation is enabled to be improved after the IMU is started.