The micro- fractures in shale reservoirs are not only the reservoir space of shale gas, but also the important channel of shale gas migration and loss. The structural characteristics of shale micro- fractures of the Longmaxi Formation in the Jiaoshiba area were determined using micro- CT, field emission scanning electron microscopy (FE- SEM) and core observations data. The opening degree of micro- fractures under different conditions (surface or formation) and their contribution to shale permeability were compared to preliminarily understand the influence of micro- fracture on the preservation of shale nanoporosity. The results show that: (1) Based on micro- CT, three sections including matrix components, high- density minerals (such as pyrite) and fractures can be distinguished in shale samples, with volume ratio of 97. 88%, 0. 88% and 1. 24%, respectively; (2) Micro- fractures are mainly isolated, slender, or zigzag bending, and have length of 3. 4~299 μm, mostly around 3. 4~20μm, with an average of 12. 44 μm; (3) The opening degree of micro- fractures in the formation is about 2. 2~30. 33 μm, with an average of 3. 97 μm, which is 36. 38% lower than the surface opening degree (average 6. 24 μm). Although the micro- fractures accounts only for 0. 7% of the total volume in the shale samples, it provides more than 70% of the permeability in the shale reservoirs. This study shows that a large amount of reticular micro- fractures developed in the Longmaxi Formation shale in JYA well is the important channels for the intensive “desorption, migration and dispersal” of shale gas along the path of “porosity, micro- fracture and fracture”. Correspondingly, the decreasing pressure of fluids resulted in deformation and closure of porosities, which is not conducive to the preservation of nano- pores. The conclusion is of great practical significance to the study of micro- fractures in shale reservoirs mainly as reservoir space or dispersal channel.