NOVELTY - A straw is washed, piled up and fermented. The fermented straw are chopped, and provided into cooking pot and processed with sodium hydroxide solution. The straw is washed to obtain cellulose and lignin. The cellulose is washed with sodium hypochlorite or chlorine-dioxide bleached. The bleached cellulose is processed with sodium hydroxide solution, to obtain sodium carboxymethyl cellulose. The sodium carboxymethyl cellulose is dried in an oven at 30-50 degrees C for 1 hour, to form dried material and to obtain white-powdered sodium carboxymethyl cellulose.    USE - Preparation of sodium carboxymethyl cellulose (claimed).    ADVANTAGE - The method enables economical preparation of sodium carboxymethyl cellulose, without environmental pollution, short stewing time, low energy consumption and reduced alkali consumption.    DETAILED DESCRIPTION - A straw is washed by soaking in immersion tank for 1 hour such that the weight ratio of straw and water is 1:3-6 and stirred to remove dirt from stalk. The straw is removed from water and provided to cleaning tank, stirred for 1 hour and soaked for 24 hours such that the weight ratio of straw and water is 1:2-4. The straw is removed from cleaning tank, piled up, stacked to width of 5 m and height of 3 m, and watered every day to keep humidity and fermented. The fermented straw is chopped and cooked. The chopped straw is placed in cylinder or pan for 1-3 hours, and provided into cooking pot and processed with sodium hydroxide solution having sodium hydroxide concentration of 5-10% at 80-100 degrees C for 3-5 hours and the ratio of sodium hydroxide solution and straw is 1:3. The straw is washed to obtain cellulose and lignin. The cellulose is washed with sodium hypochlorite or chlorine-dioxide bleached for 1-2 hours. The bleached cellulose is processed with sodium hydroxide solution at 40 degrees C or less for 50-60 minutes, to obtain sodium carboxymethyl cellulose. The sodium carboxymethyl cellulose is dried in an oven at 30-50 degrees C for 1 hour, to form dried material having water content of 1% or more and to obtain white-powdered sodium carboxymethyl cellulose.