Abstract: In order to explore the effect of chlorine dioxide（ClO₂） on controlling Eimeria tenella（E.tenella）,E.tenella was incubated with ClO₂ aqueous solution with the concentrations of 1.2,0.6,0.12,0.06,0.012 g/L,and 2.5% K₂Cr₂O₇ solution（blank control） in the experiment, and the sporulation rates of E.tenella were calculated at the 15,20,25,and 30 h of culture. In addition, 4 kinds of ClO₂ aqueous solutions with the doses of 1.2,0.6,0.3,0.15 g/L were directly administered to the chicks at 1 mL/kg according to their body weight, and the death of the flock and the damage of the intestinal tract were observed. Moreover, the chickens were taken orally with a ClO₂ aqueous solution with a concentration of 0.24 g/L and 1.0×10~5 E.tenella GD strain sporoidized oocysts to observe the anticoccidial effect of ClO₂, counting anti-coccidia index（ACI）. The results showed that the spore morphology of E.tenella changed when the ClO₂ aqueous solution with concentration of 0.12-1.2 g/L and above was cultured for more than 15-30 h, and the sporulation rate was 0. After oral administration of 1.2,0.6,0.3,and 0.15 g/L ClO₂ aqueous solution, the chicks did not die and the intestines of the body were not damaged. After oral administration of 0.24 g/L ClO₂ aqueous solution to chickens infected with E.tenella,its ACI value was 163.00,which was a moderately effective anti-coccidial drug and had a certain anticoccidial effect. The results suggested that the long-term action of high-concentration ClO₂ aqueous solution has obvious inhibitory effect on E.tenella oocysts, and the effect is stable. Direct oral administration of ClO₂ aqueous solution has obvious anti-E.tenella effect, and is non-toxic and safe.