Abstract: Based on the theoretical analysis and experimental tests, a detection method for bottom sediment thickness of bored piles is studied. Further, a penetration test system to detect the bottom sediment thickness of bored piles is developed based on the bottom sediment definition of piles and its mechanical properties. EMbedded ARM computer is used to collect data in this system, and the system control software is developed by Microsoft eMbedded Visual C++ 4.0. By detecting the interface between sediment and natural clay, the bottom sediment thickness of piles is measured. Finally, the precision and environmental requirements of the system are analyzed through field tests. The results show that the proposed method can complete accurate measurement of sediment thickness with error of only 0.01~0.09 cm and little effect on test environment.