Abstract: Fatty acid and sodium carboxymethy cellulose were used to coat arginine. Then the stability and digestibility of the rumen- protected Arginine （RP-Arg） in digestive tract of sheep were detected by artificial saliva digestion test, nylon digestion test and duodenal juice digestion test. The results showed that the release rate of RP-Arg was increased with duration of culture. After 16 h culture, the release rates of RP-Arg in saliva, rumen and duodenum were 22.16%, 31.47% and 88.85%, respectively. These results indicated that the RP-Arg had a good stability in saliva and rumen and had a good digestibility in duodenum.