The invention discloses a piston sealing structure which comprises a positioning block, wherein a step hole for containing a sealing ring and a piston rod is formed in the positioning block, a positioning groove is formed in the inner wall of the step hole, and the section of the positioning groove in the vertical direction is in an inversed V shape. The piston sealing structure further comprises a first annular sealing ring, a second annular sealing ring and a third annular sealing ring, wherein the first annular sealing ring is used for being arranged in the positioning groove and sleeved with the second annular sealing ring, and the third annular sealing ring is arranged between the first annular sealing ring and the second annular sealing ring. According to the piston sealing structure, the sectional shape of the first annular sealing ring corresponds to the sectional shape of the positioning groove, so that the first annular sealing ring can be installed in the positioning groove conveniently, then, the first annular sealing ring is sleeved with the second annular sealing ring, and the third annular sealing ring is clamped between the first annular sealing ring and the second annular sealing ring. The whole process can be performed manually, and the piston sealing structure is convenient and efficient.