The invention relates to a device for preventing sediment and scale substances from entering into a rock core. The problems of the present oil-displacing device that experimental water or oil-displacing agent is settled in an intermediate container and the rock core is plugged by the scale substances are solved. The device is characterized in that an emptying pipe (2) and an oil-displacing pipe (3) are connected with the bottom of the intermediate container (1); a filtering film (4) is wrapped on an end part of the oil-displacing pipe (3) located at one end of the intermediate container (1); a rock core clamper (10) is connected with the other end of the oil-displacing pipe (3); and the upper end of the intermediate container (1) is connected with an advection pump. The device is simple in structure, is convenient in use and is used for efficiently preventing sediment and scale substances from entering into the rock core.