Based on control equations in fluid dynamics, the main thought of oil mist process for cold heading machine is proposed according to the idea of green manufacturing. The computation fluid dynamics (CFD) software is applied to simulate the multi-phase oil mist flow in control box. The simulation results give some figures including distribution and stream line path of multi-phase flow of oil mist in the control box. The results show that the inlet position of oil mist effects on its process and three types of control box are compared, from which the best type is obtained.