Abstract: Dehydration-induced cracking of lignite is a critical geological issue affecting the slope stability of open-pit mines and the surrounding rock strength of underground roadways in eastern Inner Mongolia. However, the development characteristics of dehydration-induced fissures and their coal petrological controlling factors remain poorly understood. Lignite samples were collected from the Xiyi Mine in the Wujianfang mining area of the Erlian Basin. Fourteen fresh samples from the underground working face were cut into blocks with a thickness of 2 cm along two directions: perpendicular to bedding (10 blocks) and parallel to bedding (4 blocks). After drying in a forced-air oven at 25 ℃ for 24 h, high-resolution photography (resolution 97.2 μm/pixel) combined with Avizo image processing was employed to quantitatively extract key parameters of dehydration-induced fissures in different coal lithotypes, including fissure area proportion, aperture, orientation, and fractal dimension. The coal petrological controlling mechanisms of fissure development were systematically analyzed at both macroscopic lithotype and microscopic maceral scales. The results show that the development degree and orientation of dehydration-induced fissures are controlled by coal lithotypes. Woody-rich coal exhibits the most developed fissures, with an average fissure area proportion of 12.47%, an average aperture of 0.64 mm, and an average fractal dimension of 1.27. On sections perpendicular to bedding, fissure orientation is nearly perpendicular to the bedding plane. In thick-layer woody-rich coal, abundant delamination fissures parallel to bedding develop in addition to the primary fissures perpendicular to bedding, resulting in significantly increased fissure complexity. Detritus-rich coal shows intermediate fissure development, with an average fissure area proportion of 5.03%, an average aperture of 0.45 mm, and an average fractal dimension of 1.21; fissure orientation is also nearly perpendicular to bedding. As the area proportion of detritus-rich coal increases, the fissure area proportion, aperture, and complexity all show an increasing trend. Fusain-rich coal displays the weakest fissure development, with an average fissure area proportion of 3.16%, an average aperture of 0.32 mm, and an average fractal dimension of 1.18; fissure orientation is relatively irregular, and fissures are primarily confined to the margins, resulting mainly from the passive extension of fissures from adjacent lithotypes. On sections nearly parallel to bedding, no dominant fissure orientation is observed in any lithotype. Some fissures extend across lithotype boundaries, but their orientation commonly deflects due to differences in maceral composition. At the microscopic scale, fissure morphology is controlled by maceral composition and their spatial fabric relationships. In woody-rich coal, the continuous and uniform distribution of gelified macerals results in uniform shrinkage stress and straight fissure extension. In detritus-rich coal, the mixture of huminite and inertinite macerals produces non-uniform shrinkage stress, leading to tortuous and interlaced fissure morphology. In fusain-rich coal, the characteristic fragmented cell structure of fusinite accommodates the deformation on both sides of fissures through cumulative micro-displacement over short distances, thereby controlling fissure pinch-out. The huminite maximum reflectance of the coal seam in the study area averages 0.375%, corresponding to the immature coalification stage. Although woody-rich coal has undergone a certain degree of incipient gelification, its shrinkage driving force is significantly stronger than that of fusain-rich coal and detritus-rich coal. The results reveal the differential dehydration shrinkage behavior of different coal lithotypes and their microscopic mechanisms, providing a geological reference for slope management in open-pit lignite mines and roadway support in underground mines.