Based on the finite element analysis method to simulate the O-P hardness. Taking S45C steel as an example, comparative analysis of O-P hardness of finite element simulation and O-P hardness of instrument indentation hardness experiment, results show that difference of S45C steel’s O-P hardness between the finite element simulation and real experiment is-2.62% Accordingly seen, O-P hardness can be obtained by finite element numerical simulation method, it’s a possible way to study relations between O-P hardness and Vickers hardness based on finite element numerical simulation techniques.