Abstract: In order to get the vapor-liquid equilibrium constants under the real liquefaction conditions, the data from the fractions of coal liquefied distillation oil and different gas, such as H₂ and C₂H₆, were combined together to establish the coal liquefied oil flash distillation system through the process simulation software Aspen Plus. By using the flash-distillation system, the vapor-liquid equilibrium composition and distribution were calculated at reaction temperature and pressure. Also the rules of equilibrium constant vary with the temperature (623.15K~723.15K) and pressure (10MPa~21MPa) were explored. Furthermore, the parameters of deducing hydrocarbon equilibrium equation at high pressure were regressed. And the two variable vapor-liquid equilibrium equation specified for the Shenhua coal liquefied oil was established.