Abstract: This study aims to examine the influence of coupled thermo-hydro-mechanical processes on the stress-strain curves, mechanical properties, failure mode and damage evolution process. Using THM coupling system, triaxial compression tests were performed on the thermally-treated Beishan granite under high pore water pressure. The σ₁-ε₁ curves are basically in coincidence with each other under different pore water pressure in the preexisting micro-crack closure region and the linear elastic region, which gradually start to move towards the ε₁ axis as the cracks were initiated and propagated. Moreover, with the increase of pore water pressure, the peak strength and the corresponding axial strain decrease, while the inclination of the shear failure surface increases and the damage process evolves more quickly. It was demonstrated that the influence of pore water pressure on the rock damage and failure is mainly manifested in accelerating the process from crack growth to macro instability.