High-quality MgZnO semiconductor materials had been grown using plasma-assisted molecular beam epitaxy (P-MBE) on c-plane sapphire substrate by inserting special metal buffer layers. X-ray diffraction results show that the MgZnO films keep hexagonal structure when the mole fraction of Mg varies from 0 to 32.7%, and the full width at half maximum (FWHM) of the films are 0.08°~0.12°. To the best of our knowledge, the crystal quality should be one of the highest level ever reported. With the increasing of Mg content in the films, the room-temperature photoluminescence (PL) of ultraviolet emission peaks are shifted from 378 nm to 303 nm. A detailed study on MgZnO film by temperature-dependent photoluminescence shows that the bound exciton emitting has two different quenching processes with the temperature increasing. In addition, resonance Raman spectroscopy indicates that there is a linear relationship between the content of Mg in the films and the A(LO) phonon mode frequency shift. This relationship provides a simple and efficient method to determine Mg content in MgZnO films. It is found that Raman spectroscopy is more sensitive to the component phase change than the X-ray diffraction characterization. Finally, the temperature-dependent Raman spectroscopy was employed for MgZnO and a theoretical explanation of A (LO) and A (2LO) phonon mode frequency shift with temperature was given and discussed.