The　effect　of　the　external　mechanical　stress　on　chloride　diffusivity　in　concrete　can　be　equivalent　to　the　effect　of　porosity　change　on　chloride　diffusivity　induced　by　external　mechanical　stress.　And　based　on　this　viewpoint,　a　meso-scale　model　and　analysis　method　were　proposed　to　study　the　chloride　diffusivity　in　heterogeneous　concrete　under　compressive　stress.　In　this　approach,　the　mechanical　simulation　was　performed　first　by　using　the　meso-scale　finite　element　method.　The　outcomes　of　the　mechanical　response　of　concrete　were　then　used　as　input　data　for　the　simulation　of　chloride　diffusivity.　The　concrete　at　the　meso-scale　was　assumed　to　be　a　three-phase　composite　composed　of　aggregate,　cement　paste　matrix　and　the　interfacial　transition　zones.　The　meso-scopic　numerical　model　of　concrete　under　uniaxial　compressive　stress　was　built　to　investigate　the　chloride　diffusivity　behavior.　The　effect　of　compressive　stress　on　chloride　diffusivity　was　explored,　and　the　quantitative　relationship　between　effective　chloride　diffusion　coefficient　in　concrete　and　compressive　stress　level　was　obtained.　©　2016,　Tongji　University.　All　right　reserved.