The elastic moduli of high pressure treated supersaturated AI-LI solid solutions were measured. An interesting elastic behaviour was observed, in that, the bulk modulus decreased with an increase in the lithium content, whereas the Young’s modulus and shear modulus increased. In order to clarify this property, we investigated the compressibility of the Al-Li supersaturated solid solutions prepared by high-pressure solid-solidification by high-pressure Synchrotron X-ray diffraction. The obtained pressure-volume relations were fitted to Birch’s equation of state. The calculated bulk moduli were lower than those of pure Al at a reduction of about 0.6 GPa per mol % Li. The temperature dependence of the elastic modulus for those supersaturated solid solutions was also measured, and it was found that the trend in the variation of the elastic modulus against the lithium concentration was maintained in the temperature range of 5-290 K. Therefore the attractive relationship between the bulk modulus and Young’s modulus was demonstrated to be intrinsic.