Abstract: To investigate the heterogeneity and variation in pore connectivity of coal pores under karst landforms, taking the vertical elevation difference of different mountain bodies in karst areas as the research characteristic, six groups of coal samples with different vertical mountain elevation differences were collected from the northern Guizhou coalfield. Based on the multifractal theory, combined with high-pressure mercury intrusion test, low-temperature nitrogen adsorption and low-field nuclear magnetic resonance experiments, the multifractal characteristics of multi-scale pores in coal samples under karst landforms were analyzed, and the relationships between multifractal parameters, pore proportion and vertical principal stress were further discussed. The results show that there is a significant strong linear fitting relationship between the partition function lg χ(q,ε) and scale ε for full-scale pores of coal samples, indicating that the multi-scale pores of coal exhibit favorable multifractal behavior. Macropores and micropores have a more uniform pore size distribution, while mesopores and small pores present a more concentrated pore size distribution. A negative correlation exists between pore connectivity and heterogeneity. Micropores possess strong pore connectivity but poor pore heterogeneity, whereas mesopores show the opposite characteristics. The pore proportions of mesopores and micropores are positively correlated with the H value; the pore proportion of micropores is negatively correlated with the α₀ value, while no obvious correlation is observed between the proportion of mesopores and the α₀ value, suggesting that the mesopore size segment is not an effective factor affecting pore heterogeneity. Vertical principal stress promotes the pore connectivity and inhibits the heterogeneity of micropores respectively. With the increase of vertical principal stress, micropores exhibit weaker heterogeneity and better pore connectivity. Karst geomorphic conditions not only affect the heterogeneity and connectivity of coal pores, but affect the gas adsorption capacity of coal, thereby further influencing the enrichment law of coal reservoirs gas under such landforms. Therefore, research on the multifractal characteristics of multi-scale pores in coal samples under karst landforms can further lay a foundation for the study of gas occurrence law and safe mining of mines.