In order to solve the malfunction of magnetic seal oil leakage in an aeroengine with nondamage feature,analysis was carried out for the magnetism of magneticstationary seal ring,the vibration operating mode,the compression ratio and extension ratio of Oring in the rotor ring.The results show that the main causation of magnetic seal oil leakage are that the magnetic specific pressure is too low and the tensile stretch of Oring is over high in design.The operation reliability of magnetic seal is theoretically increased and malfunction of seal leakage is solved through the improvement design on Oring and gear shaft.