Reaction conditions for preparation of a highly substituted carboxymethylcellulose(CMC) directly from the cotton-knit-waste were determined. The cotton-knit-waste was composed of 90% of a-cellulose and less than 2% of other components, such as ash, extractives, acid soluble and insoluble part. Thus, the cotton-knit-waste was highly pure cellulose. Various grades of CMC were prepared from this cotton material under given reaction conditions. The mortar ratio of monochloroacetic acid(HCA) to cotton-knit-waste and the agitation were the most important factors determining the degree of substitution(DS) during the preparation of CMC A highly substituted CMC was obtained when the molar ratio of MCA to cotton-knit-waste was 1.9 and the agitation was 600 rpm. The viscosity in a 5% NaOH aqueous solution of the CMC prepared from cotton-knit-waste was higher than that of the commercial CMC prepared from wood pulp.