Aiming　at　the　problem　of　self-balancing　control　of　a　cubical　robot,　this　paper　researched　the　dynamic　modeling　of　the　cubical　robot　balancing　on　its　edge.　Using　the　prototype　of　cubical　robot　built　as　the　research　subject,　the　dynamic　model　was　derived　with　Lagrangian　method　and　Kane　method.　The　correctness　of　the　model　was　verified　in　theory　by　comparison　of　the　two　methods.　The　controller,　designed　based　on　the　mathematical　model,　was　used　in　balance　control　of　the　physical　cubical　robot　prototype.　The　correctness　of　the　model　was　verified　again　with　the　obtained　expect　effect.　This　dynamic　model　developed　can　provide　a　base　for　further　study　of　balance　control　of　a　cubical　robot　balancing　on　its　corner.