Pollution feature and characteristic pollutants in black liquor of red pine chemical pulping were studied to reveal the contribution of lignin in black liquor to pollution load. A UV-visible spectrometry method to determine lignin content in black liquor was established, together with the work curve of the contribution of lignin to the COD content, to explore the contribution of lignin to the COD content.It was found in the cooking process that the concentration of dissolved organic compounds in the black liquor was high with poor biodegradability and complex components. The main organic pollutants include phenolic and organic acid compounds, where the phenolic compounds have up to 84.34% relative concentration. Lignin concentration in black liquor is 65.7 g·L-1 with produced CODcr value as high as 93 640.86 mg·L-1,which accounts for about 51% of the total CODcr load in black liquor. The results show that lignin is the main source of pollution load for black liquor in traditional chemical pulping industry.