Abstract: Experimental studies on the co-pyrolysis of coal and lignin were carried out on a fixed-bed reactor to investigate the composition and transformation of the co-pyrolysis products. The results show that co-pyrolysis reduces the yield of char and promotes the yield of gas, the maximum pyrolysis gas yield increases by 33.1%. Co-pyrolysis has a significant promotion effect on the generation of CH₄ and CO with different ratios of co-pyrolysis. The interaction between the pyrolyzed volatile fractions of coal and lignin shows the most pronounced interaction at a coal to lignin mixing ratio of 1∶1, and the pyrolysis tar yield shows a positive synergistic effect. Guaiacols are converted to monophenols and bisphenols during the co-pyrolysis process, and the content of monophenols and bisphenols increase by 2.9% and 9.8%, respectively, while the content of guaiacols decreases by 5.1% compared to the theoretically calculated values. The breakage of carbonyl and carboxyl groups, and the interaction with volatile components are enhanced, which inhibits the generation of ethers, aldehydes and acids, and promotes the generation of phenols, the release of oxygenated gases and the stabilization of pyrolysis tar. The introduction of lignin into coal pyrolysis also significantly promotes the upgrading of tar, and the proportion of light components in tar is nearly 90%.