Abstract: The water-rich problem of coal seam in Jurassic coal field in northern Shaanxi Province is very special, which seriously affects the safety of mine production. According to the microstructure characteristics of No.2 water-rich coal seam in Balasu Coal Mine, northern Yuheng Mining Area, the experimental study was carried out including pore permeability analysis, scanning electron microscope, nuclear magnetic resonance and CT scanning. Comparing with other non-water-rich coal seams, the microscopic characteristics of the No.2 water-rich coal seam are found. The results show that, the porosity of No.2 coal in Balasu Mine Field is the highest, ranging from 30.16% to 31.93%, with an average of 30.89%. In addition to the common biological pores and friction pores in all coal seams, the No.2 coal seam also has erosion pores that represent active groundwater activities, and the types and quantities of micro-fractures are relatively large. The content of gravity water that can move freely in the inner pores is the highest（more than 10%）, and binding water is the main occurrence form of other internal water bodies of coal seams. For the same pore size, Balasu No.2 coal seam still has the largest advantage（16%）. Compared to No.3 coal seam in the same mine field and the No.2 coal seam in adjacent Dahaize Mine Field, No.2 coal seam in Balasu Mine Field has better microscopic pore quantity and space. It also reflects that the No.2 coal seam has the dominant medium conditions for storing and migrating groundwater.