Balancing　two-wheeled　mobile　robot　is　a　kind　of　natural　unstable　underactuated　system　with　high-rank　unstable　multi-variable　strongly　coupling　complicated　dynamic　nonlinear　property.　We　applied　Euler-Lagrange　method　for　establishing　the　MIMO　nonlinear　dynamic　model　based　on　the　balancing　two-wheeled　mobile　robot　system,　and　employed　this　model　to　analyse　the　robot＇s　pose　and　states　control.　The　direction　of　control　method　based　on　the　underactuated　system　was　discussed.　We　simulated　the　system　model　in　the　MatLab　environment,　and　got　the　in-out　responses.　Thus,　we　provide　a　certain　experimental　platform　for　the　design　of　the　balancing　controller.