The room-temperature photoluminescence (PL) spectra of hydrothermal grown ZnO film and nanowires coated with Al are investigated, which exhibit much less UV emission enhancement ratio as against that of nanowires fabricated by thermal evaporation method. A model is suggested at last to interpret the experimental results considering the influence of the defect on the contact property between metal and ZnO, which is further evidenced by the weak PL enhancement ratio of thermal evaporation grown ZnO nanowires with H2O2 treatment. (C) 2013 Optical Society of America