In　this　paper,　the　inner　boundary　conditions　of　a　simply　supported　rectangular　Mindlin　plate　with　a　finite-length　Partthrough　crack　is　first　obtained.　The　part-through　crack　on　the　plate　surface　having　an　arbitrary　length　and　depth　is　assumed　to　be　open,　non-propagating　and　parallel　to　one　side　of　the　plate.　Based　on　Mindlin　plate　theory　and　Hamilton　theory,　we　got　the　governing　equations　of　motion.　Then,　the　rectangular　plate　is　decomposed　into　two　domains　and　an　artificial　spring　with　a　varying　stiffness　along　the　crack　is　used　to　describe　the　elastic　behavior　of　the　plate　at　the　interconnection　boundaries　between　two　domains.　We　got　the　strain　energy　release　rate　(G)　through　the　stress　intensity　factor　(K).　Then,　the　rotary　discontinuity　condition　is　acquired.　After　complex　derivation,　we　obtained　the　inner　boundary　conditions　of　rectangular　cracked　Mindlin　Plate.　©　2011　IEEE.