Oil mist lubrication is currently widely used as a lubrication method now. It has some advantages as follows: low fuel consumption, uniform lubrication and high efficiency. In job site, oil mist condensation occurs in the pipeline, and this will not only reduce the efficiency, but also lead to accidents. Nowadays, CFD numerical simulation software has been widely applied in design, but the research of oil mist condensation in the transmission process based on CFD is very fare. In this paper, to choose the right the working parameters and a reasonable pipeline layout in job site, the oil mist condensation in the pipeline was simulated based on CFD. And it was found that, the diameter of oil mist particle is mainly influenced by temperature, and the best temperature range is made out.