The paper deals with the use of MATLAB and COMSOL Multiphysics environments for solution of optimization problem regarding underground thermal processes occurring at the old mining dumps affected by subsurface endogenous fires. It gives the description of measurement system and physical setup of the experimental borehole used to provide the real measured data for the model with the aim of its verification. The optimization problem is defined and solved by proposed computational technique that uses both MATLAB and COMSOL Multiphysics with the LiveLink tool that integrates these environments. Results of the optimization help to evaluate the total or relative heat power of the mass within mining dump.