The effects of axial load on the natural frequency in simply supported thick composite beams are determined using the finite element method. The material properties of the elements are calculated with two different average value methods (arithmetic and weighted average) and the effects of axial load on the natural frequency of the beam are examined. A computer program is developed to analyze the effect of axial load on the natural frequency. The finite element method is used to determine the axial load effects on the natural frequency of a fiber reinforced composite beam. The results are obtained and compared with the analytical solutions by taking different element numbers in the thickness direction. With the help of these two methods, eight-node brick elements are used in multilayer finite element analyses. It has been observed that the results obtained by the arithmetic average method are quite close to the analytic results.