Abstract: The main idea of the theory of the揹ouble effective stresses攊n porous medium proposed by Dr. LI Chuanliang is that porous Gmedium, under force, bear two stresses that are“primary effective stress”and“structural effective stress”, which controls the elastic deformation and the structural deformation, respectively. The mechanism of porous medium deformation is researched based on mechanical analysis. The result indicates that the concept of the“primary deformation”is not suitable, which may be replaced by“elastic deformation”.And the above“elastic deformation”does not depend on the“elastic effective stress”but the value of extra stress, value of intergranular contact stress, value of fluid pressure and the distribution of the above stresses; and the structural deformation does not depend on the?structural effective stress”but the value of extra stress, value of intergranular contact stress, value of fluid pressure, value of intergranular friction stress, value of intergranular bonding stress and the distribution of the above stresses. The immature and controversial theory of?double effective stresses”is apparently exaggerated