Abstract:The scanning electron microscope(SEM) is employed to study sandstone fractography under thermo- mechanical coupling effects. Through several fracture morphologies at different temperatures,such as cleavage,quasi-cleavage,fatigue,secondary and fragmentary,local ductile,intercrystalline fracture and some special fractographies,the temperature has been confirmed to influence actually micro fracture mechanism of sandstone. The fracture mechanism will transfer from brittle fracture mechanism to brittle-ductile coupling fracture mechanism with the increasing temperature. At low temperatures,the fractography of sandstone is quite smooth;but at high temperatures,the fractography is rougher,and a great deal of plastic deformation is observed obviously. Therefore,the fractography is more various and complicated after high temperature effects. The reasons can be summarized as follows. The thermal motion of mineral particle,crystals and atom will be strengthened after temperature effects;and sandstone will fracture at more widely positions. Several fracture mechanism models had been used to interpret some failure phenomena. In addition,some novel rock fractographies were reported. At last, it is concluded that any micro fractographies which has been reported in metallic fractography can also be found in rock fractography. Moreover,rock fratography is more various and more complicated because of rock own characteristics and thermal-mechanical coupling effects.