The problem of groundsill eroding is general and important for deep-water foundation in tidal reach.  Application,  technical difficulty and its settlement scheme of hydraulic pressure sensors system are introduced based on expounding the essentiality of riverbed erosion for real-time monitoring within group piled foundation. Amendment of fluctuant water level is realized by setting a sensor to monitor the tide. The sensors are fixed on the side of the piles reliably and sensor signal is transmitted smoothly with single point setting method. This method shows the characteristics of real-time,  continuity,  long-term and high precision when applied to the Su-Tong Bridge Project. Based on the results of monitoring, the mechanism of local scour within group piled foundation is analyzed.