Understanding the seepage and failure characteristics of rough fractured rock masses under thermal-hydro-mechanical(THM) coupling is crucial for exploring temperature field distribution in hydrothermal high ground temperature tunnels during construction. This study investigates the failure modes and seepage-heat transfer characteristics of sandstone through laboratory THM triaxial loading tests and multi-physical field coupling numerical simulation, considering various initial rock temperatures (25 °C, 50 °C and 75 °C) and fracture roughness coefficients (JRC). The main findings are as follows: 1) Under THM coupling, the stress-strain curves and failure modes of intact and fractured sandstones are basically consistent. The stress-strain curves exhibit 5 distinct stages: initial compaction stage, elastic deformation stage, stable crack propagation stage, rapid crack propagation stage, and post-peak stress stage. The variation pattern of permeability strain curves correspond to those of stress-strain curves. 2) Prefabricated fractures reduce the sandstone’s peak strength by about 7%. The duration of the post-peak stage decreases with the increase of JRC value, shifting failure behavior from ductile to brittle. The fracture surface angle increases with JRC, and rougher fractures are more prone to shear failure originating from the extreme points of sine curve. 3) The permeability of the fractured specimen first decreases to its minimum value during the initial loading stage, and after 2 growth stages, the permeability reaches its maximum value. In the early stage, seepage primarily occurs through the rock matrix and prefabricated fractures, while in the later stage, the expansion of prefabricated and newly developed cracks significantly broadens seepage channels, with permeability growth rates approximately 3 times higher than that of the early stage. 4) Temperature elevation significantly affects the initial and minimum permeability values but has a limited effect on the strength characteristics of the sample.