This　paper　shows　that　the　mechanical　bchavior　of　concrete　materials　can　be　described　by　a　nonlinear　Unified　strength　criterion　which　requires　four　independent　parameters　for　model　calibration.　The　criterion　covers　all　the　area　from　spatially　mobilized　plane　curve　in　the　lower　bound　to　Mises　circle　in　the　upper　bound　on　the　deviatoric　plane,　with　an　exponential　curve　on　the　meridian　plane　in　principal　stress　space.　Four　material　parameters　in　the　strength　criterion　have　their　clear　physical　meanings　and　their　determination　approaches　are　also　given.　Four　sets　of　true　triaxial　experimental　results　are　compared　with　the　modeling　results　of　the　proposed　criterion.　It　shows　that　the　proposed　criterion　is　capable　to　capture　the　characteristics　of　yielding　and　failure　and　reasonably　calculate　the　multiaxis　strength　of　concrete　materials.