Abstract: In many practical geotechnical problems,soils are always subjected to the stress path involving the principal stress rotation.A hollow cylinder apparatus(HCA) was used to study the properties on strength and pore pressure of typical Hangzhou intact clay during the variation of principal stress direction.It was revealed that due to the inherent anisotropy in structure of soils,the strength was greatly affected by the direction of the major principal stress and the parameters of intermediate principal stress but the influence of principal stress rotation(PSR) was not ecident.Shear band formed when samples failed no matter whether PSR had happened or not,meanwhile the angle between the shear band plane and direction of the major principal stress nearly kept constant.PSR could cause pore pressure accumulation due to PSR which couldn’t be neglected as compared with limiting pore pressure caused by shear with fixed stress direction,and the quantity of accumulation was decided by amplitude of rotation,value of shear stress and shear stress level.