A mathematical model for the quenching heat transfer of grinding balls was established based on the heat-conduction equation and the law of conservation of energy. The heat-conduction equation was differentiated with the finite-difference method and the boundary conditions were solved based on the volumetric method. The numerical simulation of the quenching temperature field was carried out using the MATLAB software programming. The hardness and microstructure of a grinding ball after the heat treatment were analyzed by means of a Rockwell hardness tester, OM and SEM, which were also used to verify the correctness of the simulation data. The results show that the simulation data for the quenching temperature field at a water temperature of 35°C were in good agreement with the experimental results obtained with water quenching at temperatures of 34-36°C. The hardness range for a grinding ball from the surface to the center was 59.4-57.9 HRC. The grinding ball was completely hardened and the overall martensite structure could be obtained.