Study of the phase equilibrium of natural gas components plays an important role in the designing of LNG plants. Since the problems of equilibrium in two-phase vapor-liquid systems of natural gas hydrocarbons have been extensively studied, investigations are currently focused on multiphase systems of hydrocarbons in mixtures with inorganic substances such as water, carbon dioxide, hydrogen sulfide, hydrogen, and nitrogen. This article dwells on the phase equilibrium of binary mixtures of methane, ethane, and propane with nitrogen. Depending on the ratio of the components and the thermobaric parameters, mixtures of these hydrocarbons with nitrogen may exist as mixtures of mutually soluble components or mixtures of only partially soluble components. The areas of existence of three-phase liquid-liquid-gas system were determined by calculation. The results obtained hold great importance for LNG process design and modernization.