The　strength　of　concrete　materials　can　be　described　by　the　theory　of　generalized　non-linear　strength　with　four　independent　parameters.　The　failure　surface　of　the　strength　criterion　in　the　principal-stress　space　is　smooth,　and　therefore　it　has　continuous　partial　derivatives.　The　theory　of　generalized　nonliner　strength　is　applied　as　a　yield　function,　and　the　plastic　shear　strain　is　applied　as　hardening　parameter.　The　relationship　between　shear　stress　and　plastic　shear　strain　is　split　up　into　two　function,　in　which　one　concerning　the　hardening　and　one　concerning　the　softening.　On　the　basis　of　these　assumptions,　a　three-dimensional　elastic-plastic　constitutive　model　for　concrete　is　established　in　the　study.　The　present　theoretical　results　are　comparable　to　the　available　material-test　data,　this　indicates　that　the　developed　constitutive　model　is　capable　of　describing　the　strength　and　deformation　behaviors,　also　the　strain　softening　behaviors　of　concrete.　Furthermore,　the　model　is　applicable　to　simulate　concrete　structures　under　multi-dimensional　non-linear　stress,　providing　a　basis　reference　for　structural　design　and　analysis.