<p>Pyrolysis is an important method for the clean and efficient conversion and utilization of coal. The composition characteristics of its pyrolysis products are influenced by the complex composition of the coal itself. By selectively altering the structure of coal through pretreatment, the corresponding relationship between specific structures and pyrolysis characteristics can be explored. In this paper, three different types of solvents were used to conduct solvent swelling pretreatment (SSP) on Shengli (SL) lignite. The effects of pretreatment on the structure and composition of SL coal were investigated by a series of advanced characterization methods (such as XRD, FT-IR, and NMR), and the pyrolysis characteristics of the coal samples were explored in a fluidized bed reactor. It was found that: SSP can effectively break down the weakly bonded structures in coal, exposing the oxygen cross-linked centers in coal, dissolve a large amount of oxygen-containing compounds as well as some aliphatic and aromatic substances, disrupt the cross-linked structure of coal, increase the average pore size, and reduce the aromaticity, and the mixed solvent of methanol and tetrahydrofuran shows a better pretreatment effect. The tar yield was maximally increased from 9.36 to 11.11%, the CO release was maximally raised from 1.45 to 1.66&#xa0;mmol g<Stack> _coal ⁻¹ </Stack>, and the gasification activity of semi-coke was significantly enhanced. Meanwhile, the removal of oxygen-containing functional groups with weak covalent bonds can reduce the hydrogen consumption during pyrolysis, which is conducive to the stability of other free radicals, and the yield of light tar was increased from 43.10 to 49.78%. In particular, this study elucidates the potential mechanism by which solvent swelling pretreatment affects the structure of SL lignite, thereby providing a theoretical foundation for the directional pyrolysis of lignite.</p>