We have studied the nonlinear interaction between two different eigen modes in suspended carbon nanotube resonators. It was found that the mode coupling in suspended carbon nanotubes was dominated by single electron-tunneling process. For suspended carbon nanotube resonator at low temperatures using quantum dot embedded in the nanotube as detector, the interaction was found between two different eigen modes. For nanotube resonators in the coulomb blockade regime the nonlinear modal interaction was dominated by single electron tunneling as opposed to displacement induced tension. A strongly enhanced mode coupling was observed in the coulomb blockade regime which was of the order of magnitude larger than in conventional micro resonators. The obtained results found in good agreement with previously obtained results.