<p>Grind-hardening process, which integrates grinding technology and surface hardening theory, is regarding as a promising surface strengthening approach. This process is competent to produce a hardened layer with a certain thickness on the surface. It improves the fatigue strength, wear resistance, and corrosion resistance of the engineering components, so as to meet its application in complex working conditions. However, the hardness penetration depth (HPD) often varies at different positions on the surface, which affects the application performance and service life of the parts significantly. In view of this phenomenon, a grind-hardening experimental study on AISI 1045 steel is developed firstly. Besides, the instantaneous grinding force and the final microstructure composition, distribution, and HPD are measured, respectively. Further, the temperature distribution and its change of the workpiece surface are simulated by finite element method, and the microstructure transformation of the hardened layer at different positions is studied with cellular automata model. Thus, the formation mechanism of HPD homogeneity is discovered. Finally, HPD homogeneity with different processing parameters is predicted and verified by grind-hardening experiments. The results show that a certain error between the predictive HPD and the experimental value varies from 2.1 to 12.7%, which verifies the effectiveness of the study. Moreover, the HPD is inhomogeneous with different processing parameters, and the fluctuation of grinding heat caused by unstable grinding force is the fundamental reason for this phenomenon during grind-hardening.</p>