Abstract: To explore the changes of nitric oxide(NO),nitric oxide synthase(NOS) and glutathione perxidase(GSH-Px) of blood following intratraxheal instillation of silica in rats and the effect of tea polyphneols(TP)combined with Vit C,Vit E on those biochemical indexes of rats induced by silica.Methods The contents of NO NOS and GSH-Px activities in blood of experimental rats were measured.Results Compared with the physiological saline group,the average content of NO,NOS of the silica group increased(P<0.05).The change of GSH-Px activities were a gradual decreased tendency.TP combined with Vit C,Vit E that used to treated the experimental silicosis rats could effectively decrease the level of NO NOS and increase the activities of GSH-Px.Conclusion TP combined with Vit C or Vit E can alleviate the abnormal metabolism of NO NOS in rats induced by silica.