Cellulosic fibers, as the most abundant biopolymer on earth, are attracting more and more interesting to be absorbent for ion removal from aqueous solution due to its biodegradability and renewability. In this paper, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride was used as functional agent to modify the cellulosic fibers to be absorbent for Cr (VI) in aqueous solution. Our attention in this work was aimed at the influence of mechanical refining treatment before graft on the modification as well as the absorption capability of modified fibers. The modification was carried out using refined fibers and raw fibers. The modified fibers were verified by IR analysis. The results showed that in isopropyl alcohol solution and under alkaline condition, the functional agent can be grafted onto fibers. The mechanical refining treatment of cellulosic fibers before modification can improve the grafting efficiency. The absorption capability of modified treated-fibers for Cr (VI) from aqueous solution is higher than that of modified untreated-fibers. More hydroxyl groups on the surface of fibers after mechanical refining treatment is the reason for higher absorption capability of modified treated-fibers and higher grafting efficency.