In　order　to　achieve　in-situ　growth　of　layered　double　hydroxides　(LDH)　film　on　plasma　electrolytic　oxidation　(PEO)　coating　of　AZ31B　magnesium　alloy　under　mild　conditions,　a　facile　method　was　used　in　this　work,　that　is　ethylenediaminetetraacetic　acid　(EDTA)-assisted　growth　method.　Compared　to　the　conventional　hydrothermal　method,　the　fabrication　of　LDH/PEO　composite　coating　by　this　method　does　not　require　a　high　temperature　and　high　pressure　environment　and　is　not　constrained　by　the　size　of　the　reactor.　Furthermore,　the　obtained　LDH/PEO　composite　coating　exhibits　enhanced　corrosion　protection,　which　will　be　widely　applied　in　corrosion　protection　field　of　surface　engineering.　In　this　work,　an　effective　strategy　to　control　the　dissolution　of　PEO　coating　and　the　growth　of　LDH　film　by　regulating　the　concentration　of　EDTA　was　proposed,　after　revealing　the　growth　behavior　of　LDH　on　PEO　coating　during　this　facile　fabrication　process.　The　growth　behavior　of　LDH　film　can　be　briefly　summarized　in　three　stages:　PEO　coating　dissolution,　LDH　nucleation,　and　LDH　growth.　Interestingly,　the　growth　mechanism　of　LDH　was　changed　with　EDTA　assistance.　LDH　shifted　from　preferential　growth　within　the　micropores　of　the　PEO　coating　to　uniform　growth.　With　the　assistance　of　0.06　M　EDTA,　which　is　optimal,　the　dissolution　of　original　PEO　coating　provided　a　stable　and　sufficient　Mg　source　for　the　growth　of　LDH　film,　resulting　in　a　dense　LDH　network　structure　on　the　PEO　coating.　This　uniformly　grown　LDH　film　could　not　only　seal　the　inherent　defects　of　the　PEO　coating　but　also　exhibited　the　ability　to　adsorb　corrosive　anions,　which　increases　the　tortuosity　and　difficulty　in　penetration　of　corrosive　media,　significantly　improving　the　corrosion　resistance　of　the　LDH/PEO　composite　coating.