The invention relates to a compensation hole and center valve type
brake master cylinder opening sealing structure and belongs to the technical field of automobile braking systems. The inner end of a first
piston is slidably connected with a
master cylinder body by virtue of a first contact point and a second contact point; an oil inlet hole of the
master cylinder body is positioned between the first contact point and the second contact point; a sealing ring groove is formed in the master cylinder body which is in sliding connection with the second contact point of the first
piston; the outer lip of a secondary cup is hermetically connected with the sealing ring groove, and the inner lip of the secondary cup is hermetically connected with the outer
diameter of the second contact point of the first
piston. The sealing structure disclosed by the invention has the advantages that the structure is novel, the quantity of parts is small, the probability of a failure mode occurring is reduced, and the
operational performance of the product is greatly improved; the first piston is contacted with the master cylinder body through the two contact points, and the guide distance of the first piston during moving is long, so that the motion performance of the product is stable, the sealing characteristics of the compensation hole and center valve type
brake master cylinder opening are further optimized, the product sealing performance is effectively improved, and the product weight is lightened.