In modern technology and science, "salt" has been widely used for many applications such as pharmaceutical products, battery, foods, cosmetics, and paints. Especially it is used as additives for controlling material properties. However the effect of salt on material properties is explained qualitatively and their behaviors are interpreted empirically based on observations. Thus, the molecular-level picture of salinity effects remains unclear. The purpose of this study is to reveal the physical mechanism of viscosity of aqueous solution, including sodium chlorides, and, in particular to understand anomalous behavior in the viscosity upon addition of salt. In oder to establish the physics of aqueous solution we will use viscosity and dielectric measurements complemented by inelastic X-ray scattering and molecular dynamics simulation.