A comparative analysis was conducted on the quantitative analysis methods for regenerated cellulose fibers (viscose fibers, modal fibers, lyocell fibers) and cotton blended fabrics. Nine samples of regenerated cellulose and cotton blended fabrics were evaluated according to two standards: GB/T 2910.6—2009 Textiles—Quantitative chemical analysis—Part 6: Mixtures of viscose or certain types of cupro or modal or lyocell and cotton fibres (method using formic acid and zinc chloride) and AATCC TM20A—2021e Test method for fiber analysis: Quantitative. The results indicated that for cotton/viscose and cotton/modal fibers, three method yielded results with deviations of less than 1% from the standard values, showing minimal differences. However, for cotton/lyocell fibers, the acetic acid-zinc chloride method at 40 ℃ and the 59.9% sulfuric acid method resulted in deviations between 1% and 3%, with notable differences and incomplete dissolution of lyocell fibers observed. In contrast, using the acetic acid-zinc chloride method at 70 ℃ resulted in deviations of less than 1%, indicating minimal differences.