Abstract: To further improve and deepen the understanding of the low rank coal reservoir characteristics in our country, microfracture and mineral genesis of 25 co al samples from the southern Junggar Basin of Xinjiang had been systematically analyzed based on the micro spectrophotometer, scanning electron microscopy and en ergy dispersive spectrum ( SEM- EDS) analysis. The results showed that the microfractures in the research area were well developed. Exogenous fracture heterogeneit y was much stronger than the endogenetic fracture, exogenous microfractures could indicate the complexity of regional tectonics and the posibility of the tectonic coal. The mineral content of coal samples that endogenous fractured developed was less, mainly by authigenic minerals, followed by the terrigenous clastic minerals, no epig enetic genesis minerals; however, the mineral types and content in coal sample that exogenous fissure developed was more and higher, dominated by epigenetic miner al followed by authigenic kaolinite, terrigenous clastic mineral was rare. Fluid exchange could easily occur in the exogenous microfracture, and exhibited a multi- period mineral flling. Many of the exogenous microfracture are flled with calcite, but multi- period mineral flling in endogenous microfracture is relatively small.