Linear theories are basically unable to model the dynamic behavior of nanotubes due to the large deflection/dimension ratios. In this paper the closed form expressions are obtained for the large-amplitude free vibration of nanotubes. The nonlinear governing differential-integral equation of motion is derived and solved using the Galerkin approach. The derived nonlinear differential equation is then solved using the Variational Approach (VA) and the Homotopy Analysis Method (HAM). The fundamental harmonic as well as higher-order harmonics are analytically obtained. The approximate solutions are compared with those of the numerical responses and accordingly a numerical analysis is carried out. A parametric sensitivity analysis is carried out and different effects of the physical parameters and initial conditions on the natural frequencies are examined. It is found that both the variational analysis and homotopy method are quite consistent and satisfactory techniques to analyze the vibration of nanotubes.