This paper presents a study of the full three-dimensional thermo-mechanical (TM) behavior of rock pillar in sp Pillar Stability Experiment (APSE) using a self-developed numerical code TM-EPCA3D . The transient thermal conduction function was descritized on space and time scales, and was solved by using cellular automaton (CA) method on space scale and finite difference method on time scale, respectively. The advantage of this approach is that no global, but local matrix is used so that it avoids the need to develop and solve large-scale linear equations and the complexity therein. A thermal conductivity versus stress function was proposed to reflect the effect of stress on thermal field. The temperature evolution and induced thermal stress in the pillar part during the heating and cooling processes were well simulated by the developed code. The factors that affect the modeling results were discussed. It is concluded that, the complex TM behavior of sp rock pillar is significantly influenced by the complex boundary and initial conditions. The paper presents a study of the full three-dimensional thermo-mechanical (TM) behavior of rock pillar in sp Pillar Stability Experiment (APSE) using a self-developed numerical code TM-EPCA3D. The transient thermal conduction function was descritized on space and time scales, and was solved by using cellular automaton (CA) method on space scale and finite difference method on time scale, respectively. The advantage of this approach is that no global, but local matrix is ​​used so that it avo avoids the need to develop and solve large-scale linear equations and the complexity therein. A thermal conductivity versus stress function was proposed to reflect the effect of stress on thermal field. The temperature evolution and induced thermal stress in the pillar part during the heating and cooling processes were well simulated by the developed code. The factors that affect the modeling results were discussed. It is concluded that, the complex ™ behavior of sp rock pillar is signifi cantly influenced by the complex boundary and initial conditions.