The rotational bands of even-even isotopes are studied in the frame work of variable moment of inertia (VMI) and broken polynomial (BPM) models. The predicted results of the (B.P.) model are in close agreements with experimental data and other theoretical ones. By using broken polynomial, we will calculate the energies of yrast band from low up to high energy levels including the back bending/upending region. The theoretical calculations of the different models forms are analyzed and compared with the experimental data. It is found that excitation energies can be described successfully within this model.