Abstract: To study coal reservoir nature using coal petrological approache is characteristic with investigating occurrence,shape,quantity,filling of micropore-fracture system directly.This approach is useful to find out the origin,evaluation law and its influence factors of microfracture.Micropore is divided into phyteral cell remaining pore,matrix pore and new forming pore during coalification.The microfracture system consists of butt cleat,face cleat,inherited butt cleat and joint.In this paper,the distribution,evaluation law with coalification of microfracture and their relation to coal permeability have been researched,and some new results have been obtained.