The　dynamic　model　of　flexible　two-wheeled　self-balancing　robot　is　obtained　on　the　Lagrange　equation　and　dynamics　mechanics　theory.　Use　springs　to　imitate　human　lumbar　spine.　The　linear　model　can　be　got,　state-space　equations　are　established　yet　and　the　robot　is　controlled　easily　and　effectively.　Validity　and　rationality　of　the　system　model　and　the　designed　controller　are　verified　through　the　performance　experiments　of　the　prototype　too　then　the　real　robot　has　been　done.　The　improved　Boltzmann　machine　is　used　for　controlling　robot＇s　posture　based　on　study.