We study the bearing mechanisms of the jacked pile during the pressing in sand with model test.To analyze stress changing laws of model pile while it is pressed into four different depths,we entirely measured the axial force,the displacement of model pile top,the strain of model pile top,and the circumferential strain and longitudinal strain of model pile.Using a semi-analytical and semi-numerical method,we deduced confining pressure and friction resistance according to circumferential strain and radial strain of model pile.The results show that:in the beginning of penetration,there will be negative friction in the upper part of model pile;as the penetration depth increases,the range and the values of negative friction in upper part are reduced until it disappears;pile skin friction is a smaller proportion in pile resistance,but its proportion increases with pressing depth increasing.Confining pressure increases with depth of penetration during the whole process.Confining pressure in the same depth of the soil is also increasing during the process of penetration.With the penetration depth increases,increasing trend of pile skin friction and confining pressure presents a better consistency,and the ratio between pile skin friction and confining pressure is from 0.41 to 0.53.