Abstract: Computed Tomography (CT), by which the internal change of core scan can be observed, is used more often in carbonate core test. On the basis of low-permeability sandstone cores CT scanning analysis, this paper firstly demonstrates the basic principles of Computed Tomography, and then conducts gas core test based on given test method and steps, finally does core analysis in terms of CT scanning steps from three aspects: one is the CT number of dry core; second is core porosity and distribution; and the last is CT scanning of core before and after the mechanical test. Test results show that the tighter the core, the more the CT number; the core porosity from analysis of CT test is very close to the experiment measured value; the core gives birth to diversified fractures under a certain force. Conclusion has been drawn from the results, CT scanning can diagnose the coMPact degree of cores, determine core porosity and meanwhile observe core fracture change after the core fractured, which supplies references to the study of low-permeability core fracture extension.