Abstract: The deformation characteristics and seal clearance shape of a segmented circumferential seal under fluid-structural coupling are the key factors for its stability and reliability. The fluid-structural coupling model of a dynamic segmented circumferential seal was established to study the flow field characteristics of seal clearance and the law of structural deformation. Then, the main mechanical parameters affecting the deformation of seal rings were analyzed by orthogonal experimental design, including the seal pressure difference, the initial load and stiffness of the circumferential spring, the initial load and stiffness of the axial spring. Furthermore, the influence of joint shapes, joint clearances and groove profile of the auxiliary seal interface on the deformation of seal rings were discussed. The results showed that the existence of the joint clearance had a significant effect on the pressure distribution of the flow field in the main seal interface clearance, especially a large area of low-pressure zone easily formed near the joint on the low-pressure side joint. And the existence of the low-pressure zone made the main seal interface radial clearance of the deformed single-segment seal ring showed the characteristics of being large in the middle and small at both ends along the circumferential direction. Due to the gradual decrease of the fluid film pressure along the leakage direction, and the certain bending moment produced by the axial spring force and high-pressure gas force based on the groove profile design of the auxiliary seal interface, the main seal interface radial clearance of the deformed single-segment seal ring presented a monotonously decreasing trend along the axial leakage direction. The influence of each mechanical parameter on the structural deformation of the seal rings was in descending order of the seal pressure difference, the initial load of the circumferential spring, the initial load of the axial spring, the axial spring stiffness and the circumferential spring stiffness. Through reasonable design of mechanical parameters, the deformation of a segmented circumferential seal and the clearance distribution non-uniformity of the main seal interface could be significantly reduced. Among the influence of the structure of each seal ring on its deformation, the joint shape and the groove profile of the auxiliary seal interface had great influence, while the joint clearance had relatively weak influence. The deformation characteristics of the T and H joint shapes were obviously better than those of the R and P, and the joint shape mainly affected the radial deformation at the joint of the segmented seal ring. The reduction of the joint clearance was beneficial to improve the uneven deformation of the seal ring. But there was a critical value, and when the critical value was reached, the improvement of the uneven deformation of the seal ring would be very limited if the joint clearance was continuously reduced. Adding the corresponding supporting interfaces to the groove profile design of the auxiliary seal interface could offset the bending moment caused by the axial spring force, eliminated the axial wedge-shaped clearance characteristics at the corresponding position of the main seal interface, and further improved the clearance uniformity of the main seal interface. Through the reasonable improvement of the seal ring structures, including the use of the triangular joint structure, smaller joint clearance and the groove profile of the auxiliary seal interface with axial spring support structures, the deformation of the segmented ring could be effectively controlled, and the main seal interface radial clearance with a more uniform distribution could be obtained.