In order to investigate organic pollutants in pine kraft bleaching spent liquor, high and low molecular weight compounds were isolated and examined their chemical characteristics.Following contents were clarified.1. The chlorinated oxylignin (hereinafter referred to as COL), which was prepared as one of high molecular weight compounds, amounts to approximately 16 percent of total organic materials. The molecular weight distribution measured through Gel permiation chromatography and Ultrafiltration process indicated that COL has rather higher molecular properties as compared with Milled Wood Lignin and Thio Lignin. On the other hand, chemical structure of COL was found to be seriously decomposed in the process, and further structural predominance of p-hydroxyphenylpropane unit in original lignin was almost disapeared. Taking into consideration of the existence of chlorine derivatives of vanillin in the products by alkaline cupric oxide oxydation, however, it is inferred from the fact that COL still contains a small amount of the chlorinated aromatic ring in its molecule.2. The low molecular weight compounds were obtained by continuous extraction with n-hexane, ethyl ether and ethyl acetate respectively. Each extractive was investigated by means of column chromatography, gas chromatography-mass spectrometry and chemical analysis. Consequentry, following compounds were recognized as the constituents of these extractives : Palmitic Acid, Stearic Acid, 2, 4, 6-Trichlorophenol, 5-Chlorovanillin, β-Sitosterol, p-Hydroxybenzoic Acid, Vanillic Acid, 5-Chlorovanillic Acid, 6-Chlorovanillic Acid, Syringic Acid and Ferulic Acid.