The swelling and water-retention capacity of bentonite in saline water are the important application properties of bentonite as the raw material of GCLs. In this paper, the swelling volumes and the filter loss of six kinds of Na-bentonite samples hydrated with different concentrations of NaCl, CaCl2, and MgCl2 solutions were investigated. In addition, the ion-exchange properties of raw materials, the morphology and structure analysis of the samples soaked in the salt solution were discussed. The results show that the water-retention capacity of bentonite decreases with the increase of salt concentration in aqueous solution; And at the same mass concentration, the water-retention capacity in MgCl2 solution decreases most, followed by CaCl2 and the least is NaCl. The water-retention capacity of bentonite in saline water is related with ENa+. The larger the ENa+ is, the better the chemical resistance of bentonite is.