Abstract: The paper presents one kind of brittle shale characterization method: brittle index, and introduces the determination process and procedure for the index. This method is simple to operate, and has no special requirements for sample size and shape, hence has universal significance for shale sample test. Experimental data show that the brittle index is positively correlated to porosity and specific surface area. According to measurement process, method, experimental data and literature analysis, the brittle index can characterize the extent and internal structure of porosity, especially the potential application for micro pores and cracks. The prospects for the application of brittle index in the studies of shale internal structure and gas desorption are discussed preliminarily.