Abstract: The paper studied the effect of different level of cobalt sulfate on fresh grass yield and nutrient quality of alfalfa by leaf surface spurting. The result indicated that, Spurting cobalt sulfate could remarkably (P < 0.05) increase the fresh grass yield of alfalfa and the leaf stem ratio (LS). The effect of the concentration of 300 mg/kg treatment is best, in compared to CK treatment, the fresh grass yield increased by 25%. Different levels of cobalt sulfate affect the nutrient content differently. The contents of crude protein (CP) and P was increased with the applied Co amount increased, while there was on significantly different on content of crude fiber (CF), nitrogen free extract (NFE), crude ash (CA), and the content of crude fat (CF) was decreased with the applied Co amount increased. When the Co concentration was 300 mg/kg, the yield of crude protein (CP), crude ash (CA), P, NFE was reach max., among the all of treatment, and significantly higher than that of CK treatment, the yield of crude fiber and Ca of treatment Co2 was reach max., but there were no significantly different to CK. and crude fat was Co1 treatment.