Experiments were performed to grind scrap tire peels into fine powders in the cryogenic grinding process. The temperature distribution within a scrap tire peel was calculated by a numerical method of transient heat transfer. The optimal temperature of the compressed air in the vortex mill was also found by experiments and compared with calculated results. Calculations were in good agreements with the corresponding experimental data. The proposed calculating method may be applied in the design of the cryogenic grinding process for recovering the cold-energy stored in the fine powders.