Electronic　health　(e-health)　social　system　provides　an　effective　way　for　the　patients　to　share　their　treatment　experience,　exchange　medical　information　and　build　a　supportive　relationship.　In　this　paper,　we　propose　a　novel　symptom-matching　based　group　key　management　scheme　for　the　e-health　social　system　supporting　dynamic　group　membership　change.　The　patients　in　this　system　are　diagnosed　and　treated　by　different　medical　institutions.　This　proposed　schemes　allows　a　group　of　patients　from　different　healthcare　domains　(cross-domain)　to　securely　establish　a　group　session　key　to　protect　the　group　disease　discussion.　The　scheme　supports　patient　anonymity　and　traceability　since　the　identities　of　the　patients　are　hidden　in　an　anonym　and　their　medical　institution　is　able　to　recover　the　real　identity.　The　group　agreement　protocol　ensures　that　only　the　authenticated　patient　with　the　same　symptom　could　derive　the　group　session　key.　The　privacy　of　patient＇s　symptom　is　also　protected　since　the　patient　cannot　know　the　other　patients＇　symptoms　if　they　do　not　have　the　same　symptom.　The　security　of　this　scheme　is　proved　and　the　performance　is　evaluated　theoretically　and　experimentally.　The　simulation　and　comparison　indicate　that　our　scheme　has　good　performance　and　suitable　for　the　mobile　e-health　social　system.　(C)　2017　Elsevier　B.V.　All　rights　reserved.