Abstract: The strengh experiment is carried out to the unsaturated soil of Luoyang area on the improved triaxial apparatus.The result indicates that the rate and change range of φSr are larger than the ones of φ’,and the values of cSr and φSr fast increases along with the fall of Sr.It is difficult to study the strength theory of unsaturated soil,in which the influences of mechanical factors and structure of soil on the strength and deformation theory are comprehensively considered.The generalized dual-variable strength theory of unsaturated soil is established based on the saturation which is taken as a control variable.The conclusion indicates that the attempt is effective,which is different from the other theories because of consideration of the influences of mechanical factors and structure of soil.