The　formation　and　evolution　of　Gd-rich　precipitates　companying　with　the　matrix　structure　ordering　in　a　Mg97Gd2Cd1(at.％)solid-solution　alloy　aged　at　200　℃　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.)→　B19-type　ordered　domains　→　D019-type　ordered　domains.Four　Gd(Cd)-rich　precipitates,G.P.Ⅰ　zone,G.P.Ⅱ　zone,β＇and　β1　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　β＇precipitates　and　promoting　the　forming　ability　of　theβ1precipitate.