:In order to further enhance the dynamic pressure effect of fluid film on the end face of dry gas seal,a new dry gas seal with combined groove face was proposed. The combined groove is composed of two adjacent spiral grooves which are partially overlapped in the circumferential direction,including a long spiral groove and a short spiral groove,and the groove depth and radial length of the two grooves are different. The mathematical model of the combined groove seal was established,and the sealing characteristics were analyzed by finite difference method. The results show that when the end clearance is less than 1.5 μm,the opening force of the fluid film of the combined groove seal is larger than that of the tra- ditional groove seal,and the smaller the clearance,the greater the difference of opening force between the two seals. The leakage of the combined groove seal is larger than that of the traditional groove seal,but the leakage is much smaller than the design value. The film stiffness of the combined groove seal is significantly larger than that of the traditional groove seal when the clearance is less than 3.5 μm,and the smaller the clearance,the greater the difference of film stiffness between the two seals. In view of the end face film of combined groove has greater stiffness,opening force and leakage ratio when the clearance is small under the condition that the leakage of the combined groove seal does not exceed the standard value, so the comprehensive performance of the combined groove seal is significantly superior to the conventional groove seal.