Nanocrystalline TiO2 thin films were prepared by sol-gel method and were then used to fabricate metal-semiconductor-metal ultraviolet photodetectors with Au Schottky contact. It was found that dark current of the fabricated devices was only 1.9 nA at 5 V applied bias. High responsivity of 199 A/W was achieved when it was irradiated by the ultraviolet light (λ=260 nm). The low dark current and high responsivity maybe attributed to the effect of Schottky barrier in company with neutral semiconductor owing to the wide finger gap of 20 μm. The devices show a slow time response with a rise time of 6 s and a decay time of 15 s. The authors deduced that the slow time response was caused by defect traps which were widely distributed in nanocrysal.