A mechanical seal with circular YBCO superconducting blocks embedded in the static ring was designed,utilizing the low temperature condition of the rocket engine turbine pump mechanical seal.This mechanical seal generates both dynamic pressure liquid membrane force and superconducting magnetic repulsion force between the static and dynamic rings during operation,which can increase the axial bearing capacity of the mechanical seal face and avoid wear under small gaps.Based on the superconducting magnetic force calculation model and magnetic repulsive force detection system,the variation of superconducting magnetic force of YBCO block with gaps was studied theoretically and experimentally.The calculation model of the mechanical seal performance with superconducting magnetic force was established,and the opening force,leakage,film thickness and friction resistance moment of the magnetic fluid composite mechanical seal were simulated.The results show that the designed YBCO superconducting block can provide 784 N to 896 N superconducting magnetic force for the mechanical seal at a gap from 5 μm to 30 μm.At the speeds from 10 000 r/min to 35 000 r/min, the opening force of the mechanical seal with superconducting magnetic force increases by 896 N on average,the leakage increases by 0.72 mL/s on average,the film thickness increases by 2.8 μm on average,and the friction resistance torque decreases by 0.47 N·m on average.The increase in bearing capacity and film thickness,as well as the decrease in friction resistance moment,helps to reduce the wear of mechanical seals caused by starting and stopping under extreme working conditions,thereby improving their lifespan.