In accordance with coal sample observation by scanning electron microscope (SEM) and researches based on such subjects as anthracology, tectonic geology and material mechanics, the endokinetic fractures in coal are further classified into dewatering fractures, condense fractures and static pressure fractures, while the exogenetic fractures are further divided into tensile fractures, pressure fractures, shrink fractures and slack fractures, consistent with the development regularity of the geometric shapes, sizes and arrangement of fractures. The evolution, identification and controlling factors of the microfractures in coal are discussed, and the role of various fractures in coal reservoir is also analyzed. The researches on coal microfractures are of great significance in the study of coal reservoir, the exploration and development of coalbed methane, and the drainage of coal gas from coal mines.