In this study, sub-harmonic displacement of nonlinear oscillations with parametric excitation is solved using a simulation method called the Differential Transformation Method (DTM). We employed this method to derive solutions of nonlinear oscillations with parametric excitation equation. Also Runge-Kutta as numerical method is exerted to this equation too. The obtained results from DTM are compared with those from the numerical solution to verify the accuracy of the proposed method. The results specify that the technique introduced here is accurate and achieve suitable results in predicting the solution of such problems.