Mg_xZn_(1x)O films with hexagonal structure are prepared by RF magnetron sputtering(RFMS) on Si substrates.Transmission spectra demonstrate that the absorption edge of Mg_xZn_(1-x)O film has a remarkable blue shift from 378 nm to 308 nm compared with ZnO film,which shows that the band gap increases with the increase of Mg content in Mg_xZn_(1-x)O film.The analysis of SEM energy spectrum displays that Mg content in Mg_xZn_(1x)O film is larger than that in the sputtering source.The photoluminescence(PL) spectra illustrate that the blue emission peak appears at wavelength 431 nm when excited by light of wavelength 260 nm.With the increase of wavelength of the excitation light from 280 nm to 300 nm,monochromatic blue and green emission peaks are generated at wavelength 459 nm and 489 nm respectively,and emission intensity shows a distinct increase in contrast to that of the emission peak at 431 nm.These PL peaks may be related to the oxygen vacancies in Mg_xZn_(1-x)O film.