Abstract: Methane hydrate (MH) is an important clean energy resource, widely distributed in clayey type methane hydrate bearing sediment (MHBS) in the South China Sea. The mechanical behavior of clayey type MHBS is affected by many factors, such as temperature fields, back pressure fields, chemical fields, pore size, MH saturation, physicochemical properties of clay, which is significantly different from that of sandy type MHBS. Therefore, the development of numerical analysis methods reflecting the mechanical response of clayey type MHBS under complex loading paths is crucial for the safe exploitation of MH. This work establishes a semi-theoretical equation of strength and stiffness of MH considering pore size and physicochemical properties by introducing the potential of water, and then this equation is introduced into the existing contact model of structural clay. The algorithm of the pore size is developed by the initial fabric parameters associated with the contact model, and the isotropic compression tests, the conventional triaxial tests and the true triaxial tests are conducted, and the effect of MH saturation, temperature and physicochemical characteristics (represented by water content) on mechanical behavior of clayey type MHBS are analyzed. The results show that the simulation results are consistent with those of experiments. Higher MH saturation and water content, as well as lower temperatures increase the yield strength and peak strength of clayey type MHBS, and higher MH saturation will significantly enhance shear dilation of clayey type MHBS. The true triaxial tests show that the hardening rule and the critical state strength are closely related to the principal stress coefficient.