The invention relates to silting preventing devices, and discloses a seabed silting preventing device and a silting preventing method for the device. The seabed silting preventing device comprises a seabed crawler (1), and an installing plate (7) is fixedly arranged on the upper surface of the seabed crawler (1) and provided with a large water turbine (8) and a small water turbine (9). The large water turbine (8) comprises first blades (80), wherein the first blades (80) are of a hollow structure, inner cavities (800) of the first blades (80) are formed and are flaky cavities, water inlet grooves (801) are formed in the front faces of the first blades (80), a plurality of water outlet holes (802) are formed in the back faces of the first blades (80), and the water inlet grooves (801) and the water outlet holes (802) communicate with the cavities (800). Through secondary disturbance of the large water turbine and the small water turbine, after stable tides pass through the rotating large water turbine blades, the flow speed and the flow direction of the stable tides can change, the flow line can generate disturbance, and the disturbed tide flow line can show rotation and fluctuation.