Abstract: Taking the surrounding rock with an internal cavity as the research object, considering the influence of the major factors, such as rock fracture, porosity and permeability of rock, theoretical studies on the gas seepage problem are carried out. Based on the Darcy’s law, analytical formulas for some important parameters of the gas seepage problem in the surrounding rock with an internal cavity, mainly including the amount of gas permeability and the arrival time of the gas seepage, are derived. The relevant experiments on gas seepage in granite are performed, in which, the TNT explosive charge is exploded in the center cavity of the granite, and taking the detonation product CO as the trace gas, the amount of gas permeability and the arrival time of the gas seepage are obtained. Using the derived formulas, the amount of gas permeability and the arrival time of the gas seepage under the same condition are calculated. The results show that calculating these parameters by using the formulas is a precise and effective way. Also, it is a rapid way, and for this reason, it is really functional for emergency issues of practical projects. Meanwhile, the analytical formulas derived according to theoretical analysis may provide important reference for the validation of numerical results and for the design of experimental studies.