In　this　paper,　by　introducing　a　chemical　field,　the　J-integral　formulation　is　presented　for　the　chemo-mechanical　coupled　medium　based　on　the　laws　of　thermodynamics.　A　finite　element　implementation　of　the　J-integral　was　performed　to　study　the　mode　I　chemo-mechanical　coupled　fracture　problem.　For　derivation　of　the　coupled　J-integral,　the　equivalent　domain　integral　(EDI)　method　was　applied　to　obtain　the　mode　I　J-integral,　with　expression　of　the　area　integrals　based　on　constitutive　relationships　of　a　linear　elastic　small　deformation　for　chemo-mechanical　coupling,　instead　of　the　finite　deformation　problem.　A　finite　element　procedure　is　developed　to　compute　the　mode　I　J-integral,　and　numerical　simulation　of　the　y-direction　stress　field　is　studied　by　a　subroutine　UEL　(User　defined　element)　developed　in　ABAQUS　software.　Accuracy　of　the　numerical　results　obtained　using　the　mode　I　J-integral　was　verified　by　comparing　them　to　a　well-established　model　based　on　linear　elastic　fracture　mechanics　(LEFM).　Furthermore,　a　numerical　example　was　presented　to　illustrate　path-independence　of　the　formulated　J-integral　for　a　chemo-mechanical　coupled　specimen　under　different　boundary　conditions,　showing　a　high　accuracy　and　reliability　of　the　present　method.　The　variation　laws　of　J-integral　and　the　y-direction　stress　field　with　external　chemical,　mechanical　loading　and　time　are　revealed.　The　J-integral　value　increases　with　larger　external　concentration　loading　in　the　same　integral　domain.　The　extent　of　diffusion　is　much　greater　with　larger　concentration,　which　leads　to　a　stronger　coupling　effect　due　to　the　chemical　field.　This　work　provides　new　insights　into　the　fracture　mechanics　for　the　chemo-mechanical　coupled　medium.