The Nano-TiO 2 was modified by doping TiO 2 nanoparticles with W 6+ as catalyst, improving the photocatalytic activity and photocatalytic properties of nanometer TiO 2 . We have studied the tungsten doped TiO 2 nanoparticles’ photocatalytic degradation performance and viscosity reduction properties to the polymer by the degradation of polyacrylamide in oilfield sewage (PAM). Different catalysts, different amount of catalyst and PAM aqueous solution’s pH value effect the photocatalytic degradation rate. The results show that: tungsten doped nanometer TiO 2 has higher photocatalytic activity than the TiO 2 nanoparticles and its photocatalytic performance of viscosity reduction is very significant. The oil-field sewage degradation rate reached about 70% after 120min light reaction of 125 W high pressure mercury lamp as the light source with 3%tungsten doping amount and 1% photocatalyst dosage. TiO 2 nano-particles doped with tungsten had obvious viscosity reduction effect on the photolytic oxidation of oilfield wastewater containing PAM.