Ca-Mg-Al type layered double hydroxide (LDH) was synthesized using mixed solutions containing Ca2+ and Mg2+ as divalent cations by a co-precipitation method. The removal of anionic species in aqueous solution such as As(III), B, Cr(VI) and Se(IV) was examined with the reaction products obtained. The effects of Mg2+ -Ca2+ mixing ratio on the physical properties of the products and their ability to remove anionic species were investigated. Aluminum hydroxide (AH) and hydrotalcite-like compounds (HT) were formed at pH 10 by a precipitation reaction. In the co-precipitation operation, Mg2+ and Al3+ were completely precipitated at pH 10, while the percentage of Ca2+ precipitated was extremely low. The ability of the complex of AH and HT to remove B and As(III) was higher than those of AH and HT alone. For all anionic species, 90% or higher removal was achieved with the products synthesized from the solution at the mixing ratio of Ca2+ : Mg2+ = 1 : 1. Hydrocalumite-like compounds (HC) and HT were also produced at pH 12. All amounts of Mg2+ and Al3+, and 70-80% of Ca2+ were precipitated at pH 12 to form LDH products. Products containing both HC and HT showed no increase in the removal ability in comparison with HC and HT alone. The order of solubility of the product in an anion removal operation was as follows: HC >> HT > AH. The products obtained from the Ca2+ -Mg2+ mixed solution, namely the complexes of AH and HT or HC and HT, had higher solubility than those of HC, HT and AH. The product containing HT as a main component was consider to be superior in the removal of anionic species and the stability of LDH structure among those obtained in Ca2+ -Mg2+ -Al3+ mixed solution.