A　unified　expression　describing　the　nonlinear　characteristics　of　strengths　of　various　materials　on　the　π　plane　and　the　meridian　plane　is　used　in　the　generalized　nonlinear　strength　theory.　Thus　a　brand　new　system　of　the　nonlinear　strength　theory　is　formed.　The　nonlinear　strength　theory　is　developed　from　the　single　nonlinear　strength　theory　which　can　be　just　suitable　to　a　certain　material　to　the　generalized　nonlinear　strength　theory　which　can　be　suitable　to　various　materials.　Therefore,　the　system　of　strength　theory　is　completed.　The　generalized　nonlinear　strength　theory　includes　a　series　of　the　single　nonlinear　strength　theories　which　have　already　existed　and　might　appear　in　the　future,　such　as　Mises＇s　criterion,　SMP　criterion,　etc..　The　superiority　of　the　system　of　the　generalized　nonlinear　strength　which　is　suitable　to　various　of　materials　is　verified　by　the　strength　tests　on　clay,　rock　and　concrete.