The study of the startup process is of great significance to the smooth opening of dry gas seal by using carbon dioxide with impurities as the lubricating medium.Keeping the closing force constant,and adjusting the rotational speed to balance the opening force and closing force of the dry gas seal,the relationship between the rotational speed,leakage rate and equilibrium film thickness during the start-up process of the dry gas seal lubricated by carbon dioxide with impurities was studied.The effect of the inlet pressure and inlet temperature on the opening critical rotational speed and leakage rate of the dry gas seal,as well as the influence of balance ratio on the closing force were discussed.The results indicate that the contact force of dry gas seal decrease rapidly with the increasing of the equilibrium film thickness,while the operating speed and leakage rate of dry gas seal increase with the increasing of the equilibrium film thickness.Under the same equilibrium film thickness,the required operating speed increases and the leakage rate decreases correspondingly as the impurity content in carbon dioxide grows.When the inlet pressure is lower,the dry gas seal is easier to open,and at the same time,the calculation case with more impurities is the easiest to open.It is conducive for the opening of dry gas seal to moderately lower the inlet temperature of lubricating medium,and at the same inlet temperature,the higher the impurity content in carbon dioxide gas,the more difficult it is to open the dry gas seal.When the balance ratio is adjusted to a proper value,the dry gas seal can realize the static pressure opening,and it is easier to achieve the static pressure opening when the carbon dioxide gas contains impurities.