To study the inhibiting effects of S-Nitroso-Glutathione (GSNO) on sporulation process of Eimeria tenella (E. tenella) oocysts by detecting the sporulation rate, GSNO as nitric oxide donor was used to treatE. tenella oocysts sporulated for different times; Several kinds of antioxidants and oxidants were used to investigate the inhibitory effects of GSNO on sporogony process of E. tenellaoocysts. The results showed that GSNO still inhibited the oocysts sporulated 10 h, but had few inhibiting effect on the oocysts sporulated for 14 h; the antioxidants, such as Vitamin C (VC), mannitol and sodium salicylate, could not eliminate the inhibitory effects of GSNO on oocysts; neither did the ferrous sulfate (FeSO4) nor Dithiothreitol (DTT). However, the oxidants, potassium dichromate (K2Cr2O7) and potassium permanganate (KMnO4) could obviously repress the effects of GSNO on oocysts. At present, the inhibitory mechanism of GSNO on unsporulated oocysts was still unclear.