The invention discloses an underwater on-line monitoring equipment anti-scour method and device. The relation of water flow impacting force and the included angle of the water flow direction and an equipment chocked flow face and the relation of the height of the chocked flow face and the water flow speed are obtained based on a hydraulics theory, and therefore the corresponding relation between the water flow impacting force and the included angle is obtained. In the field, the included angle between the water flow direction and the equipment chocked flow face is changed so that the water flow impacting force can be adjusted, and the anti-scour device which can adjust the included angle between the water flow direction and the equipment chocked flow face is designed according to the anti-scour method. The underwater on-line monitoring equipment anti-scour method is simple and easy to achieve, the anti-scour device is simple in structure and convenient to operate, underwater on-line monitoring equipment is made to be adaptive to changeable water flow environments through the method and device, and the water flow scour prevention capacity is improved.