Coocus laccae(Laccifer lacca Kerr), usually known as Lac, is a kind of cocoon which is parasitic on the tree around India and China. It contains the laconic acid of red colored dyes and has been used for cosmetic or natural dyeing prior to the introduction of New World cochineal. Nevertheless, the characterization of lac has not been studied, very little informed. The purpose of this study is to examine the effects of dyeing conditions fur Lac extract, such as pH of dye bath, concentration of Lac exact dyeing temperature and time, to find out the optimum conditions. The results were as follow. 1. The highest K/S values of the silk and wool was shown at PH 3 and PH 4. 2. K/S values of the silk came to nearly the adsorption equilibrium state at 40$^{circ}C$ and the curve of wool showed a dramatic increase with the increase of temperature. 3. Dyed silk and wool fabrics showed good light fastness without using mordants.