Abstract: In order to explore the effects of urea on the feed efficiency, rumen fistula sheep was used as test animal to study the effects of urea concentration gradients on the degradability of feed in the sheep rumen and the content changes of main nutrients by using nylon-bag method. Three rumen fistula sheep were selected as test animals. Control group （no urea） and test groups（adding 1%, 2%, 3%, 4% and 5% urea） were set. The content of crude fat,crude fiber,ash,crude protein,calcium and total degradation rate in the 6th , 12th , 24th hour in rumen were measured. The results showed that the feed degradability at the addition level of 2% and 3% was significantly higher than that of control group and 5% urea group, which indicated that suitable amount of urea could promote the utilization rate of feed nutrients. Adding 2% and 3% urea could promote the early-period utilization rate of calcium in feed and adding 3% and 4% urea could promote the early-period utilization rate of ash in the feed.