Thermal effect plays a crucial role in governing rock strength and deformation behaviors when exposed to high temperatures. This paper presents a novel thermal-mechanical failure criterion for rocks considering the thermal effect from a micromechanical perspective. Based on linear elastic fracture mechanics, a thermal-mechanical failure criterion is established from a micromechanical perspective considering the thermal effect, and the criterion coincides with the mathematical form of the classical Hoek-Brown criterion. The new failure criterion includes four independent parameters with physical meanings. Meanwhile, the closed expression of the material constant m is derived with physical meanings, which vary with temperature. Finally, the proposed failure criterion is validated by comparing theoretical predictions and experimental data. The proposed analytical model provides an effective means by which to predict the non-linear behavior of rocks with and without confining pressures.