Imperata cylindrica (L.) Beauv, commonly known as alang-alang (in Indonesia) is a perennial grass which broadly distributed in South Kalimantan, Indonesia. This grass is a noxious weed both in crops and natural areas, causing serious economic and environmental damage. Exploitation and utilization of Imperata cylindrica could be a practical proposition for the managing of this wild plant and also for novel low cost source of chemical feedstocks. The objective of present study was to isolate cellulose from Imperata cylindrica and synthesis of sodium carboxylmethyl cellulose (Na-CMC) from it. Na-CMC is cellulosederived material which widely use in many industrial application, such as thickner, binder, and stabilizers for food and pharmaceutics. The isolated cellulose from Imperata cylindrica was converted to Na-CMC by alkalization and etherification method using different sodium hydroxide (NaOH) concentrations (5% - 25%) and ratio of monochloroacetic acid (MCA) to cellulose (0.6 - 1.4). The optimum condition for synthesis was found to be 15% NaOH and the ratio of MCA to cellulose 0.80 which provided the highest solubility and degree of substitution. The carboxymethylation process of cellulose was confirmed by Fourier transform infrared spectroscopy (FTIR). In addition, changes in crystallinity of cellulose and Na-CMC was evaluated by X-ray diffraction (XRD). Keywords: alang-alang, Imperata cylindrica, carboxymethyl cellulose