Abstract: For the rail tank wagon, an analysis is made to the issues that top-unloading oil of vacuum unloading system will produce tail gas from vacuum pump and air-lock due to high temperature. A technical reform method is presented for the vacuum unloading oil system. Based on the experiment and investigation, a technical reform program for the vacuum unloading oil system is designed. Field application shows that an immersible pump method is the most ideal method for the oil vacuum unloading system of rail tank wagon.