Abstract: Application of the principle of hard and soft acids and bases(HSAB) to salting-out effect in solvent extraction by neutral extractants is discussed in this paper. The salting-out effect of cations is a function of their classification in "types of acid". The salting-out effect of the hard acid cations increases with the increasing of PA. Hard acid and borderline acids have different mechanisms in salting-out effect. The salting-out effect of Li+ and H+ is also discussed in the present work.