Abstract：Experiments are carried out to study coarse sandstone on upper plane of coal bed of Fangzhuang Coal Mine of Jiaozuo Co.，Ltd. under conventional triaxial compression by the MTS815.03 servo-controlled testing machine after high temperature. Based on the experimental results，the macro-mechanical properties of coarse sandstone under conventional triaxial compression after different temperatures are investigated. The relationships between triaxial compression strength，average modulus，cohesion，internal friction angle and peak strain of coarse sandstone and temperature are analyzed；and those between strength，average modulus and temperature are also studied. The results show that，when the confining pressure imposed on coarse sandstone is constant，and the temperature changes from 25 ℃ to 300 ℃，with the increasing of the temperature，the triaxial compression strength，average modulus，cohesion，internal friction angle all gradually increase，but the peak strain has a slightly decrease. The thermal stress generated by high temperature has an effect of absorbing deformation and closure of fracture，parts of the original fracture get close；the number of fractures decreases；the compaction rate uprates；the contact relationship of mineral grain has been improved；and the frictional characteristic has been enhanced. When the temperature is over 300 ℃，with the increase of temperature，the triaxial compression strength，average modulus，cohesion，internal friction angle all decrease；but the peak strain has a little increase. And the discordant thermal expansion which happens across mineral particles can induce structural thermal stress due to the different thermal expansion coefficients of mineral particles in coarse sandstone. Then the microcracks develop inside the sample which makes the bearing capacity and non-deformability decrease. And the confining pressure can improve the mechanical properties of coarse sandstone. When the temperature is internal，with the increase of confining pressure，the strength，average modulus，cohesion，internal friction angle of coarse sandstone gradually increase.
