A new amino acid ionic liquid, [C(3)mim][Glu] (1-methyl-3-propylimidazolium glutamic acid salt), was prepared by a neutralization method and characterized by H-1 NMR and TA. Using an Anton Paar model DMA 4500 oscillating U-tube densitometer, the densities of aqueous [C(3)mim][Glu] were measured over mole fraction of IL from 0.039 to 0.543 in the temperature range of T = (283.15 to 338.15) K at intervals of 5 K. Values of the apparent molar volumes of aqueous [C(3)mim][Glu] were calculated and were treated by Pitzer-Simonson (PS) equation, Pitzer-Simonson-Clegg (PSC) equation, and the simplified PSC equation. In comparison with the values of PS and the simplified PSC parameters, the PSC parameters have a smaller standard deviation. Obviously, when the number of parameters augments, the fitting accuracy increases.