The specialshaped sealing structure was applied to the seal of the piston of the automobile caliper disc brake.According to the elastic fluid dynamic pressure model in the fluid dynamics of the sealing interface,the quasionedimensional flow Reynolds equation of the brake fluid oil film was obtained,and the calculation method was given about the oil film thickness and leakage amount when the brake piston reciprocates.Using Fluent software,the influence of factors such as friction coefficient,brake pressure and compression on the oil film thickness and brake fluid leakage were compared and analyzed during the reciprocating process of the brake piston specialshaped sealing quincunxring and the standard sealing Oring.The results show that the oil film thickness of specialshaped sealing quincunxring and the Oring sealing are increased with the increase of the friction coefficient,and decreased with the increase of the brake fluid pressure and the compression amount,but specialshaped sealing quincunxring has better lubricity and smaller leakage under the same friction conditions.The change of oil film thickness of specialshaped sealing quincunxring is relatively slow compared with the Oring,which reduces the wear on the sealing ring.In the case of large compression,the antileakage capability of the brake piston specialshaped sealing is greater than that of the conventional standard sealing Oring.The brake piston with a specialshaped sealing structure can effectively reduce the wear of the sealing ring,has good antileakage ability and can achieve good selfsealing.