In　this　paper,　a　J-integral　formula　and　numerical　calculation　method　are　presented,　which　confirm　the　path-independence　of　a　J-integral,　considering　the　mixed-mode　fracture　in　a　chemo-mechanical　coupled　medium.　The　Jk-integral　denotes　a　two-dimensional　vector　consisting　of　the　components　J1　and　J2.　Using　the　Equivalent　Domain　Integral　(EDI)　method,　the　chemo-mechanical　coupled　J2-integral,　with　an　equivalent　domain　form　that　includes　both　a　surface　integral　and　a　line　integral,　is　deduced　using　a　poroelastical　model.　Based　on　a　semi-analytical　method,　an　auxiliary　J¯2-integral　is　derived　to　develop　a　finite　element　calculation　program.　By　choosing　two　characteristic　lengths,　near　the　crack　tip,　the　mixed-mode　fracture　parameters,　KI,　KII　and　Ts　(T　stress)　at　the　crack　tip,　can　be　calculated.　The　mixed-mode　fracture　problems,　which　are　related　to　center-cracked　and　edge-cracked　plates,　are　numerically　studied　for　certain　chemo-mechanical　coupled　boundary　conditions.　The　accuracy　of　this　method　is　verified　with　numerical　examples,　which　shows　the　path-independence　of　the　J-integral　for　chemo-mechanical　coupling.　The　stress　fields　of　two　different　cracked　hydrogel　plates　are　analyzed　with　different　boundary　conditions　under　the　chemo-mechanical　coupled　mixed-mode　fracture.　This　work　provides　new　insights　into　the　mixed-mode　fracture　mechanics　of　a　chemo-mechanical　coupled　medium.　©　2020