Abstract: A study on the application of ¹H-NMR spectroscopy to the determination of purity of triclosan (TCS), by using acrylamide as internal standard and DMSO-d₆ as solvent, was made, and the ¹H-NMR spectrum was obtained under the conditions of time of pulse delay of 20 s and scanning time of 64. H-11 (δ 6.88) and δ 5.59 were selected as the quantitative peaks for the sample and the internal standard. Averages of integrals of the peak areas were taken and used for calculation of purity of TCS by the formula given. As shown by the result, linear relationship was obtained between values of mass ratios of sample (m_r) to internal standard (m_s) ranged between 1.01 and 10.16 and respective values of ratios of integrals of peak areas of sample (A_r) to internal standard (A_s). Six portions of a same TCS sample were taken and analyzed by ¹H-NMR in parallel, values of ratios of peak areas of samples to internal standard were taken, and value of RSD (n=6) found was 0.12%. A TCS sample was analyzed by the proposed method for its purity, and average value of the results (n=3) found was 99.78%, which was in consistency with the results found by mass balance method (99.81%).