Abstract: The lubrication effect of high-speed rail gear box is very important to the running stability of high-speed rail. In this paper, the influence of different structure parameters on the lubrication effect of gearbox was studied by numerical simulation experiments. The results show that the average volume fraction of oil on the oil collecting box plane decreases while the average oil velocity increases. When the radial distance increases, the oil volume in the oil collecting box increases, but the oil velocity decreases. Proper increase of the wheelbase can improve the lubrication effect of the output end bearing, however, if the increase is too much, it may lead to oil mixing loss. The width of the oil guide bar has a significant influence on the lubrication effect of the plane of the oil collecting box. Increasing the width of the oil guide bar will increase the volume fraction of the oil, but reduce the oil speed. In order to achieve the best lubrication effect, the relevant parameters need to be optimized and adjusted according to the actual working conditions and lubrication requirements, which can extend the service life and improve the overall performance of the mechanical equipment.