A stable Ca preparation in solution form even at high concentration is provided. The aqueous preparation of Ca includes water, Ca, compounds of Formula I and Formula II. Most of Ca is in non-ionic form and forms a complex. In the complex, Ca binds to the compound(s) of Formula I and/or Formula II in a state that basic structures of them are kept. At least partially, the complex forms colloidal particles. The aqueous preparation is transparent. pH is equal to or higher than that of slightly acid；[A1, A2, A3, A4, A5 and A6 are independently O− or OX. X represents a monovalent or polyvalent cation].
