A new zwitterion containing 1,1,3,3-tetramethylguanidine was synthesized using a simple method, and the physicochemical properties as well as the crystal structure of the compound were also studied. Two new acidic ionic liquids (ILs) were synthesized using the zwitterion as the precursor and the physicochemical properties including density, viscosity, thermal property, and acidic scale of the ILs were investigated. A density functional theory investigation of the geometrical structures and electronic properties of the guanidinium triflate ionic liquid was also presented for better understanding the new ILs.