A softwood Kraft black liquor was acidified with carbon dioxide at different temperatures. The effect of temperature on the recovery yield, the content of inorganics and carbohydrates was investigated. The chemical structure of lignin was determined by GPC, IC, elemental analyzer and TG analyzer. The results showed that a higher temperature was negative to lignin precipitation. The recovery yield of lignin decreased with the temperature increase. However, the lignin, obtained at the higher temperature, had lower ash and carbohydrate contents, and a higher purity. With the increase of temperature, the molecular weight and methoxyl group content of lignin increased, while the phenolic hydroxyl group decreased. TG and DTG curves indicated that the higher acidification temperature resulted in the larger weight loss rate and smaller solid residue mass.