In view of safety aspects of hydraulic structures and waterways caused by erosion and siltation, underwater mud silting monitoring has become an important task in structural health monitoring. This paper introduces feasibility study of the scour depth determination based on lateral soil pressure measurement. Sensors which are made of FBG are used as the sensing element, whose front side is under soil pressure, and back side is under the water pressure. It can accurately monitor the lateral soil pressure by measuring the front and back pressure difference. The pressure in the horizontal direction is only water pressure in water, while it consists of lateral earth pressure and pore water pressure in soil. Therefore, it can calculates the scour and siltation depth according to the measured values given by the sensor probes placed at different depths and positions. The method can do feedback of erosion and siltation of the hydraulic structures in time during calculating analysis, and provide reliable data for the safe operation of hydraulic structures.