Abstract: The microscopic pore structure of coal reconstructed by X-ray μCT is extremely complex. The pore network model (PNM) can simplify its spatial network structure from topology. In order to quantitatively characterize the space structure of coal micro-pore by this method, X-ray μCT scanning was performed on low-rank coal in the Ordos Basin. The spatial structure model of coal micro-pores was reconstructed. The PNM spatial topology structure was constructed. The structural characteristics of its pores and throats were analyzed. The results show that: larger micro-cracks are developed inside lignite. There are few micro-cracks in gas coal, but there are many pores, large volume and high homogeneity. Pores with a volume greater than 0.25μm3 in YCW lignite account for 23%, and pores with a radius of 0.1~0.7μm account for more than 90%. Its average coordination number is 7, and the average equivalent radius and length of the throat are 0.13μm and 1.69μm, respectively. However, the pore volume of XG gas coal is mainly distributed in 0~0.06μm3, and the equivalent radius is mainly distributed in 0.11~0.26μm. Its average coordination number is 4, and the average equivalent radius and length of the throat are 0.09μm and 0.63μm, respectively. Pores in lignite has larger volume and stronger connectivity. Its throats are wider and longer. This is the essential reason for its strong permeability.