The study on the effect of drainage conditions on clay strength was carried out with double fold linear strain path triaxial test controlled by maximum drainage volumetric strain. The results show that under the condition of double fold linear strain path,the peak shear strength is merely linear to the maximum drainage volumetric strain of soil. In the whole test the sample does not reach the critical state. The effect of volumetric strain and shear strain on shear characteristic are related to shear strength level.