In this study, a novel approach based on the elliptic balance method is proposed for the first time to find the approximate frequency of nano/micro-electro-mechanical systems (N/MEMSs) modeled as the Euler-Bernoulli beams under the effect of electrostatic and van der Waals interaction forces. Firstly, the governing equation of the beam is reduced to the single-mode vibration equation using the Galerkin method. A nonlinear differential equation for the time dependent beam deflection is obtained. The authors have presented-the approximate solution as an elliptic cosine function, which considers the free term contributing to the solution. This free term is relevant for vibrations having a non-zero mean in time in which the beam is affected by a relatively large, applied voltage. By some manipulations, the obtained result is an algebraic equation with only one unknown in three unknowns: the free, vibration coefficient terms and modulus quantity of the elliptic cosine function. This nonlinear equation is solved using the Newton - Raphson method. Numerical results from the elliptic balance method show that the accuracy of the solution responses in time and approximate frequency is relatively accurate, almost coinciding with the results obtained from the numerical solution method using the Runge - Kutta algorithm. Our result also agrees well with previously published experimental and simulation results. The result is meaningful when determining the frequency of the vibrating beam with high accuracy for micro/nano systems.