Abstract: Abstract:The nano-SnOz sample was synthesized by direct precipitation of tin tetrachloride(SnC14)and sodium hydroxide(NaOH) at 92 0C temperature and a series of SnOz samples with different characters were obtained by calcined at different temperatures. The effects of calcination temperature on characters of SnOz and photodegrada- tion of methylene blue(MB) under UV-light(254 nm) irradiation have been investigated. The SnOz sample cal- tined at 200 0C showed the highest degradation rate of MB. When the calcination temperature is over 200 0C，with increasing calcination temperature the particle size of SnOz increases and the specific area of SnOz decreases，so the degradation rates of MB are decrease. The photocatalytic degradation kinetics was analyzed in detail，which was found fitting a pseudo-first-order kinetics and the Langmuir-Hinshelwood model. In UV/SnOz system the hydroxyl radicals OH·play a critical role in the degradation of MB，inducing the complete mineralization of MB to carbon dioxide，water and mineral acid.