Accurate and rapid calculation of the friction power consumption of dry gas seal is conducive to the design,operation and performance monitoring of dry gas sealThe interfacial frictional torque times the rotational angular velocity is the friction power consumptionThe concept of equivalent clearance was presented based on the idea of equal volume of the clearanceIt means the volume of equivalent clearance equals the volume of actual clearanceAccording to equivalent clearance,the calculation formula of the interfacial frictional torque of the mechanical seals with grooved faces was obtained by using Newtons law of shear directlyTaking spiral groove dry gas seal as an example,the calculation result of this formula was compared with that of Muijdermans formula,Gabriels formula and Sedys formulaThe results show that the proposed calculation method proposed is more accurate than the Sedys method and the deviation of this method is decreased significantly with the increasing of operating thicknessIn the common range of 3μm to 5μm of operating thickness of dry gas seal,the proposed calculation method has sufficient accuracy.