Highly c-axis oriented Mg0.05Zn0.95O thin films were fabricated on Si(111) substrates at different temperature by pulsed laser deposition. The influence of the substrate temperature on the structure and luminescent properties of Mg0.05Zn0.95O thin films were studied by XRD and photoluminescence (PL) spectra and the relationship between the crystalline quality and PL properties of thin films was discussed. The results indicate that the Mg0.05Zn0.95O thin films grown at substrate temperature of 450℃ show good c-axis orientation and strong PL peaks. Different PL spectra are acquired at room temperature using xenon lamps as excitation light sources，with excitation wavelengths of 240, 300 and 325nm, respectively. The UV peaks and violet peaks were found to originate from free excition radiation recombination and the PL intensity was related to crystalline quality, and the blue-green peaks may be related to the oxygen vacancies. We also discuss the physical mechanism throngh which the substrate temperature affects the red shift and blue shift of UV PL peaks.