To explore the effects of fertilization on physiological and biochemical parameters in the blood of the Wumeng semi-fine wool sheep and select the optimum fertilizer type, we carried out fertilization and grazing experiments on the perennial artificial grassland in Wumeng Prairie. The content of mineral elements in soil, forage and animal tissues was analyzed by atomic emission spectrometry. The blood parameters were analyzed by automatic blood cell analyzer and the blood biochemical parameters were detected by automatic biochemical analyzer. The results showed that fertilization significantly increased nitrogen content (P<0.01), but there was no significant difference between different fertilization treatments. Ammonium sulfate substantially increased the sulfur content of forage (P<0.01) and dramatically decreased the selenium content of forage (P<0.01). At the end of the grazing experiment, the content of copper, iron and selenium in the blood of the Wumeng sheep in the grassland enriched with ammonium sulfate was significantly lower than that in the grassland enriched with ammonium nitrate and the control group (P<0.01), and the sulfur content in the blood of the animals was obviously higher than that in the prairie enriched with ammonium nitrate and the control group (P<0.01). Ammonium sulfate fertilization evidently reduced the hemoglobin and erythrocyte hematocrit capacity of the sheep (P<0.01), while serum ceruloplasmin content, serum superoxide dismutase activity, serum glutathione peroxidase activity and serum catalase activity were significantly lower than that in the prairie enriched with ammonium nitrate and the control group (P<0.01). There were no significant differences in other trace elements, blood parameters and serum biochemical parameters between the fertilization treatment and the control group. Consequently, it is concluded that ammonium sulfate fertilization inhibit the metabolism of trace elements and decline some of the blood physiological and biochemical parameters in the sheep, which has a negative effect on their health, so we have suggested that the use of ammonium sulfate fertilizer should be reduced in pastures with low selenium, iron and copper contents.