In order to develop low-cost ZnO ultraviolet photodetectors with high performance and simple structure, in this paper,ZnO nanoparticles were prepared by a solution method.The morphol ogy,crystalline structure and optical properties of ZnO nanoparticles were investigated by field emission scan ning electron microscopy (FESEM),X-ray diffractometer (XRD),ultraviolet-visible (UV-Vis) spectrophot ometer and fluorescence spectroscopy,respectively.The experimental results show that the sampl es are nanoparticles with spherical shape, their size distribution ranges from 6nm to 8.5nm,and the average diameter of Z nO nanoparticles with hexagonal wurtzite structure is 7.1nm.A sharp absorption edge at about 370nm can be observed,and both a strong near edge emission peak at 390nm and a broad visible light emission band can be found.Moreover ,using the as-prepared ZnO nanoparticles,an ultraviolet photodetector was fabricated on the fluorine tin o xide coated glass substrate (FTO) patterned interdigital electrodes.Both the current-voltage and current-time ch aracteristics of the ultraviolet photodetector were examined in the dark and under 365nm UV illumina tion.The results display that the sensitivity,photoresponsivity,response time and recovery time of the photo detector are 62.4at －3.5V,13.6A/W at +5V,15s,and 79s,respectively.In addition,the photoresponse mechan ism of the ultraviolet detector is mainly that the oxygen adsorbed on the surface of ZnO nanoparticles plays a cent ral role.