This study is a fundamental research on the natural Polygoum tinctoria dyeing to quantify scientifically and satisfy the reproducibility of the procedure. By dyeing the silk fabrics, the establishment of accurate dyeing method was sought. At the same time, we tried to modify the traditional dyeing methods, broaden the methods, and apply the dyeing variously. The dyeability and color changes were compared and reviewed according to the changes in the reducing temperature, reducing time, concentration of the reducing agent, dyeing temperature, dyeing time, concentration of NaOH, and the number of repetition of dyeing. The optimum conditions in the dyeing procedure are as follows: Added concentration of the reducing agent is 3g/${ell}$. Reducing temperature is $60^{circ}C$. Reducing time is 40minutes. Dyeing temperature is $30^{circ}C$. Added concentration of NaOH is 1g/${ell}$. Dyeing time is 30minutes.