In this paper, we demonstrate two methods by which the aluminum content in AlxGa0.51−xIn0.49P and Si-doped AlxGa0.51−xIn0.49P film deposited on GaAs substrates by MOVCD can be measured nondestructively. The first method is to calculate the Al content by means of effective medium approximation theory based on the optical parameters of the samples determined from ellipsometric spectrometry at room temperature for different wavelengths. The second method is to obtain the values of the energy gap Eg by analyzing the third derivatives of the imaginary part of the dielectric function. The aluminum content in the samples is then evaluated by substituting the value of Eg into the inear interpolation equation. The results of both methods agreed well with that obtained by the energy dispersive X-ray analysis method.