Abstract: To explore the intrinsic relationship between rock mechanical properties and infrared radi⁃ ation，an infrared monitoring test of the entire process of uniaxial loading of sandstone was carried out. The stress change rate was introduced to characterize the transient instability of the stress field，and the infra⁃ red radiation count was used as the core quantitative indicator for the evolution of the infrared radiation temperature field. The abnormal characteristics of stress and infrared radiation during the brittle fracture process of sandstone were studied，as well as the quantitative relationship between the two physical quanti⁃ ties. The results show that by calculating the stress change rate，the stress changes can be classified into three types. Type I is a small sudden change，Type Ⅱ is a medium-sized sudden change，and Type Ⅲ is a large sudden change. Among them，Type Ⅱ sudden changes account for 82.0%. The situation where the in⁃ frared radiation count and the stress change rate simultaneously change reached 76.8%，and the infrared radiation count responded most sensitively to the Type II sudden change of the stress change rate. After fit⁃ ting the cumulative infrared radiation count before the peak stress and the stress，it was found that the stress and the cumulative infrared radiation count show a highly linear positive correlation (correlation coef⁃ficient >0.98). Analyzing the relationship between the rock brittleness index and the temperature abnormal area in the infrared thermal image，it was found that when the brittleness index is ≤0.425，the temperature abnormal area during the sandstone failure is mainly a cooling area；when the brittleness index is >0.425， the temperature abnormal area is mainly a heating area；the maximum value of the infrared radiation count after the peak is strongly positively correlated with the brittleness index，with a correlation coefficient of 0.916，providing a basis for the infrared quantitative analysis of brittle rocks.

Key words: sandstone, uniaxial compression, infrared radiation, brittle fracture, quantitative analy? sis