Zn1-xMgx O films have been grown on silicon at various substrate temperatures by pulsed laser deposition. The structural and photoluminescent properties of films as a function of substrate temperature have been studied.The optimized substrate temperature is 650℃. The x-ray diffraction spectra indicate that the films are highly C-axis oriented, and no phase separation is observed. The crystal grain size of the films is about 100nm as examined by atomic force microscopy. The cross-sectional transmission electron microscopy verified the C-axis orientation of the Zn1-xMgxO. These films showed ultraviolet photoluminescence at room temperature. The near-band-edge emission peak of the Zn1-xMgxO film deposited at 600℃ has a blueshift (0.40eV) larger than that of the film deposited at 500 ℃ (0.33eV). The ratio of the near-band-edge to defect level peak intensity is as large as 159.