Abstract: Plant cellulosic materials are a large kind of natural polymeric compounds which have abundant source and significant uses. Carboxymethyl Cellulose(CMC) is used not only in industries of fabric, medicine and food but also in drilling muds. CMC can be produced in our country, but the quality of domestic products is not good enough to use in mud oil. In present work, the hydrophilic monomer, AAM, was grafted onto cellulose by pre-irradiation technology, and than the grafted cellulose was reacted with ClCH_2 COONa. The CMC grafted with AAM have pretty good mud and physico-chemical properties which can compare with the high quality CMC Drispac, made in USA.The experimental conditions and mechanism were discussed as well.