Zinc oxide thin films have been obtained on a Si (111) substrate with a GaN buffer layer and Si (111) substrate by pulsed laser deposition (PLD),respectively.GaN buffer layer was achieved by a two-step method.The structure,surface morphology,composition and optical properties of ZnO thin films are investigated by XRD,FESEM,IR absorption spectra and PL spectra.The scanning electron microscopy (SEM) images indicate that the flower-like grains were presented on the surface of ZnO thin films grown on GaN/Si (111) substrate,while the ZnO thin films grown on Si (111) substrate show the morphology of inclination column.PL spectrum reveals that the efficiency of UV emission of ZnO thin film fabricated on GaN buffer layer is high,and that the defect emission of ZnO thin film derived from Zni and VO is low.The results demonstrate that the GaN buffer layer is significantly better than Si(111) substrate for fabricating high quality ZnO thin film by PLD technics.