Based on analysis of flow field of the rotary seal using sealing ring, mechanical models under the condition of full film friction and mixed film friction were established respectively.The influence of friction state of the sealing ring on seal performance was also discussed.The relation between force characteristic and structural parameters of the sealing ring was analyzed.Analytical results indicate that friction state mainly depends on structural parameters of the sealing ring.The expression of calculating friction torque under the condition of mixed film friction was deduced.Experiment verification had been done.Experimental results agree with the deducing theoretical conclusions on the whole.It lays the foundation for design of new type of sealing ring used in composite transmission.