Heat conduction oil ,as a kind of high efficiency and energy-efficient of the heat transfer medium, has been widely using in all kinds of chemical process units.Based on the practical application of the heat conduction oil in the company, its using characteristics, the role of expansion tank to its normal operation, controlling and operation key points and prevention metamorphism measures were introduced in details, which could provide the reference and  suggestions for the heat conduction oil system running smoothly for a long time and prolonging its service life.