Abstract: This paper presents a new instrument, Sliding-Micrometer-ISETH, and its application to determination of negative friction of piles. This instrument is now used to determine negative friction and horizontal displacement of steel pipe piles for a huge power station in East of China. Eight month’s measurements demonstrate that this instrument is specially suitable for long-term measurement of variety of geotechnical engineering. In the case of stack load with a high of 4.6m, the measured maximum axial load is about 800 KN with the rising rate of 30 KN per month, whose critical value will be lower than that calculated according to effective stresses and approximate to that, if additional pore pressure is considered. The bending stress is higher than allowable stress, and the horizontal displacement is over 600 mm in a pile located at boundary of stack area. A comparison analysis is made for measured results with the data of ground settlement, horizontal displacement and pore pressure.