On the basis of the test of the maceral and the lowtemperature liquid nitrogen specific areas of 58 coal samples which are derived from different areas and different horizons, the results depict the micropore characters of coal reservoirs in aspects of the specific areas, the morphologic character of the adsorption curve, the distribution of the pore configuration and the FHH fractal feature. Meanwhile, using the causal chain of the "specific area-porosity configuration-substantial composition and chemical structure of coal", the character of micropores, coal rank, maceral and the relationship between the mineral component and its type in the variation range of coal rank are analyzed. At the beginning, while Ro=0.60%~1.91%, the specific area and FHH fractal obviously decrease, then when Ro approaches 1.3%, these increase slightly, meanwhile, the schort's hysteresis loop of adsorption curve and the pressure scale which corresponds to fractal scale decrease obviously, and the "inkbottle" pore type with 3~4 nm aperture diameter obviously decrease or even disappear, becoming the main contributor to the decrease of the specific area. In the condition of similar coal rank, fusinite contributes more to specific area than the vitreous coal component in the eastern margin of Ordos Basin. When the content of clay mineral is more than 10%, the "inkbottle" pore type with 3~4 nm aperture diameter apparently contributes to the specific area, and the influence will be more correlated with the increase of the coal rank.