The　formation　and　evolution　of　Gd-rich　precipitates　companying　with　the　matrix　structure　ordering　in　a　Mg　97　Gd　2　Cd　1　(at.%)　solid-solution　alloy　aged　at　200　degrees　C　have　been　systemically　investigated　using　high-angle　annular　dark-field　scanning　transmission　electron　microscopy　(HAADF-STEM).　The　results　show　that　Gd-rich　precipitation　dynamics　during　the　aging　treatment　are　noticeably　affected　by　a　continuous　ordering　transformation　in　the　matrix.　The　ordering　transformation　process　involving　mainly　re-distribution　of　Cd　atoms　was　revealed　to　occur　in　the　following　way:　random　super-saturated　solid　solution　(S.S.S.S.)　-＞　B　19　-type　ordered　domains　-＞　D0　19　-type　ordered　domains.　Four　Gd(Cd)-rich　precipitates,　G.P.　I　zone,　G.P.　II　zone,　13＇　and　131　phases,　have　been　observed　to　be　formed　in　sequence　to　coexist　with　the　various　ordered　domains.　Based　on　the　HAADF-STEM　characterization　on　the　aging　microstructures　at　different　aging　stages,　it　can　be　concluded　that　the　Cd-addition　and　related　matrix　structure　ordering　can　play　significant　roles　in　modifying　the　early-stage　G.P.　zone　structure,　altering　the　morphology　of　13＇　precipitates　and　promoting　the　forming　ability　of　the　131　precipitate.　(c)　2021　Chongqing　University.　Publishing　services　provided　by　Elsevier　B.V.　on　behalf　of　KeAi　Communications　Co.　Ltd.　This　is　an　open　access　article　under　the　CC　BY-NC-ND　license　(　http://creativecommons.org/licenses/by-nc-nd/4.0/　)　Peer　review　under　responsibility　of　Chongqing　University