Here, we present a strategy for rapid measurement of gas solubility in ionic liquids based on a simple configuration of tube-in-tube reactor. Ionic liquids can be rapidly saturated without direct contact of gas and liquid via a semipermeable Teflon AF-2400 inner tubing in the reactor, and the gas solubility can be easily determined by a steady-state flux balance of both gas and liquid flowing into the reactor. Solubility data of gaseous carbon dioxide (CO2), ethylene (C2H4), and ethane (C2H6) in several ionic liquids ([Emim]­[NTf2], [Omim]­[NTf2], [Bmim]­[BF4], [Bmim]­[PF6], and [Omim]­[NTf2]) were successfully determined at temperatures between 30 °C and 60 °C and low pressure (no higher than 8 bar), showing less than 8% deviation, compared with the literature values. A single gas solubility data point can be obtained within 10 min, showing high efficiency compared with conventional methods (5–48 h). Finally, the application scope and limitations of this method were discussed.