Considering connectivity rate and spacing of fractures, volume fractions of pore matrix and fractured material in a representative element volume (REV), a method for determining the equivalent cohesion and internal friction angle is proposed under the condition of thermo-hydro-mechanical-migratory coupling. While the equivalent internal friction angle of the medium is assumed to be a constant, the equivalent cohesion will be a function of inherent cohesion, equivalent plastic strain, suction, solute concentration and temperature. A hypothetical disposal model for nuclear waste located in unsaturated dual-pore-fracture rock mass is analyzed and simulated with the proposed method. The results show that the enhancement for the equivalent cohesion by suction is larger than the weakening effect by equivalent plastic strain and solute concentration. The plastic zones in the surrounding rock mass reduce with the increasing of equivalent cohesion. Thus the distributions and values of rock mass stress, pressure and flow velocity of pore water and fracture water, solute concentration in pore and fracture also change correspondingly.