The　majority　of　existing　studies　on　the　strain　rate　effect　of　concrete　have　concentrated　on　the　dynamic　uniaxial　strength　or　a　narrow　range　of　strain　rates.　However,　concrete　material　always　works　under　a　multiaxial　stress　state　and　suffers　from　loads　with　different　strain　rates.　This　paper　presents　a　method　to　describe　the　dynamic　multiaxial　strength　of　concrete　at　all　strain　rates.　The　advantages　of　the　nonlinear　unified　strength　criterion　(NUSC)　are　that　this　factor　can　reasonably　describe　the　static　strength　behavior　of　concrete　under　a　multiaxial　stress　state.　In　addition,　the　dynamic　uniaxial　S　criterion　can　express　the　actual　dynamic　uniaxial　strength　at　all　strain　rates.　A　nonlinear　dynamic　multiaxial　strength　criterion　is　developed　based　on　the　strain　rate-dependent　strength　parameters　of　the　NUSC,　in　which　the　strain　rate-dependent　strength　parameters　are　derived　from　the　S　criterion.　The　obtained　strength　criterion　consists　of　a　series　of　continuous　smooth　convex　surfaces　in　the　principal　stress　space,　which　extends　outward　with　increasing　strain　rate.　In　addition,　the　strength　curve　gradually　changes　from　a　curved　triangle　to　a　von　Mises　circle　with　increasing　strain　rate　in　the　deviatoric　plane.　The　proposed　criterion　is　verified　via　its　application　to　extensive　experimental　data　from　multiaxial　dynamic　tests　in　the　literature,　and　the　results　demonstrate　that　the　proposed　criterion　can　reasonably　describe　the　multiaxial　strength　and　reflect　the　ultimate　dynamic　strength　of　concrete.