Two SO3H-functionalized ionic liquids (ILs), N-isobutyl-3-sulfopropan-1-aminium hydrogen sulfate [IBAC3S]HSO4 and N-isobutyl-4-sulfobutan-1-aminium hydrogen sulfate [IBAC4S]HSO4, were synthesized and characterized by NMR and HR-MS. The thermal properties and acidities were analyzed. Density, dynamic viscosity, surface tension, conductivity, and refractive index of the IL were studied as a function of temperature. The physicochemical properties, namely molecular volume, isobaric coefficients of thermal expansion, standard entropy, critical temperature, molar free volume, interstice volume, etc. of the IL were estimated according to the reported empirical and thermodynamic equations. On the basis of the Walden rule, the ionicty of the two SO3H-functionalized ionic liquids was assessed by the product of molar conductivity and viscosity.