The invention provides a method for recovering
magnesium from a
cobalt and
magnesium contained solution in
cobalt-
nickel industry for preparation of
magnesium hydroxide. The method comprises following working procedures: working procedure one: the
cobalt and magnesium contained solution is taken, the pH value is regulated through addition of 3-6 mol / L of
sodium hydroxide, a
mixed solution is subjected to
temperature control and stirred, and cobalt is enabled to be precipitated sufficiently; working procedure two: the
mixed solution is filtered, first filtrate and a first
filter cake are obtained, the first
filter cake is pulpified through addition of water, filtering is performed again, and second filtrate is obtained; working procedure three: the second filtrate and the first filtrate are mixed, third filtrate is obtained, a
sodium sulfide solution is added, a
mixed solution is subjected to
temperature control and stirred, then
polyaluminum chloride is added, filtering is performed again, and fourth filtrate is obtained; working procedure four: the fourth filtrate is added to an alkaline solution, the pH value is regulated, and
temperature control and stirring are performed; working procedure five: aging and filtering are performed sequentially, and a third filtrate cake is obtained; working procedure six: the third filtrate cake is pulpified, washed and filtered, and a fourth
filter cake is obtained; working procedure seven: the fourth filter cake is pulpified, washed, filtered, dried and smashed, and a finished product is obtained. With the adoption of the method, magnesium can be recovered in a cobalt-
nickel production process simply and efficiently for preparation of magnesium
hydroxide.