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.　The　suitable　states　and　applied　Euler-Lagrange　method　for　establishing　the　MIMO　nonlinear　dynamic　model　were　chosen　based　on　the　balancing　two-wheeled　mobile　robot　system,　and　this　model　was　employed　to　analyze　the　robot＇s　pose　and　states　control　in　different　tasks.　The　direction　of　control　method　based　on　the　underactuated　system　was　discussed.　The　system　model　in　the　MATLAB　environment　was　simulated,　and　the　in-out　responses　were　got.　Thus,　a　more　perfect　experimental　platform　for　the　design　of　the　balancing　controller　was　provided.