Abstract: Dry gas seal is a new type of shaft end seal that uses slotted sealing technology for gas sealing, and it belongs to non-contact sealing technology. Because of its high sealing properties, it is widely used in some precision equipment, such as aerospace engines. The contact between the friction end faces of the dry gas seal usually occurs in the start and stop stage, but in actual situations, due to processing errors and external environment excitation, it also lead to local vibration contact between the dynamic and static rings, then cause friction vibration of the entire end face, and reduce the sealing performance of the dry gas seal. In the past, the research on the contact characteristics of dry gas seals used the research method from micro to macro. First, the contact model of the asperity was established, and then the contact of the asperity was equivalent to the entire contact interface through probability statistics. However, they only considered the complete elastic deformation stage and the complete plastic deformation stage in the research process, while ignoring the most complex elastic-plastic stage in the asperity deformation stage, and finally the established model was inconsistent with the experimental value and had a large error. In order to explore the contact characteristics of the dry gas seal friction interface in all stages of deformation, the fractal theory and the micro-contact mechanics theory with unique characterization were used in this study. In the variable elastic-plastic deformation stage, the contact model of the asperity deformation in all stages was established through the cosine function. The established model conformed to the continuous smooth deformation theory and realized the continuous smooth transition between complete elasticity and complete plasticity. Then, a full-stage contact model of the friction interface of the dry gas seal was established by the island area theory in the fractal theory. Then the established model was compared with three classical contact models, GW model, KE model and ZMC model, and related experimental data, which verified the rationality and correctness of the contact model in this study. Finally, the effects of the real contact area, fractal dimension and feature scale on the contact characteristics of the dry-gas seal friction interface were discussed. The model results showed that the contact characteristics of the dry gas seal friction interface were related to the fractal dimension, the feature scale and the real contact area of the two surfaces. Both the dimensionless contact load and the dimensionless contact stiffness were positively correlated with the fractal dimension and the dimensionless real contact area, and their magnitudes were also positively correlated with the fractal dimension. When the fractal dimension was small, the dimensionless contact stiffness increased slowly close in magnitude. However, when the fractal dimension was large, the contact stiffness of the dimensionless contact increased nonlinearly, the gap between the orders of magnitude also increased gradually, and the variation range of the contact load of the dimensionless contact was relatively large. Both the dimensionless contact load and the dimensionless contact stiffness were negatively correlated with the feature scale. When the feature scale increased by an order of magnitude, the variation range of the dimensionless contact load and the dimensionless contact stiffness was within an order of magnitude.