In this work, we study a semiconductor-based photocatalyst MoO3synthesized using three simple techniques, including as-prepared, hydrothermaland microwave-assisted methods. The obtained samples were characterized usingX-ray diffraction (XRD), and Raman spectroscopy. We found a better crystallinityin the nanoparticles synthesized by the microwave-assisted method in comparisonto those synthesized by the other methods. From this starting result, we chosethe microwave-assisted method as a favored one to further investigate the effect ofannealed temperatures on the phase formation. In addition, by using the correlationmethod, we predicted the Raman active modes of αMoO3. The results are in goodagreement with those obtained by experiments for the same system