The study on phase behavior and physical properties of natural gas has great significance for its safe exploitation and transportation. Consequently, we studied the phase equilibria of the methane + ethane gas mixture in this work. The hydrate formation conditions (gas–liquid–hydrate equilibria) of the methane + ethane gas mixture were measured first in pure water. Then the gas solubility (gas–liquid equilibria) of the gas mixture in water was measured with/without hydrate. Finally, the bubble point and dew point (vapor–liquid equilibria) and the hydrate formation conditions and gas solubility in the presence of hydrate were calculated. The results show that before hydrate formation, the gas solubility in water decreases with temperature and increases with pressure. However, after hydrate formation, the gas solubility increases with temperature and decreases with pressure. The calculation models in this work have satisfactory accuracy for phase equilibria prediction of the methane + ethane gas mixture. Therefore, it has a good guiding significance for describing the phase behavior of natural gas.