Abstract: In this paper, a series of n·g hydraulic gradient tests have been done to study the shaft resistances of vertically loaded piles in different loading ways. The loading ways include: compressive loading on pile top, tensile loading on pile top and tensile loading on pile bottom. The experimental results include the relationship between shaft resistance and settlement, the distribution of shaft resistance intensity along pile and the relationship between shaft resistance intensity and displacement. The experimental results have, to a certain extent, revealed the mechanism of shaft resistance.