The invention relates to a wheel structure of a jack, belonging to the technical field of hydraulic hoisting industry. The wheel structure comprises a wheel frame and a wheel body, wherein the wheel frame comprises a seat disc and a pair of wheel arms, and a screw rod is arranged in the center position of the seat disc; and the wheel body is arranged between the pair of wheel arms. The wheel structure is characterized in that a rolling ball groove is arranged at the edge part on a chassis and on one side with the back to the wheel arms, a group of rolling balls are arranged in the groove, a protective cover is matched and arranged on the chassis, a screw rod abdication hole is formed at the center of the protective cover, a rolling ball concave path is arranged at the edge part of the protective cover and in the position corresponding to the rolling balls, and the screw rod penetrates through the screw rod abdication hole and is equipped with a nut; and wheel body shaft holes are respectively formed on the pair of wheel arms and in the positions which correspond to each other, a wheel body shaft is arranged in the pair of wheel body shaft holes by penetration, the wheel body is arranged on the wheel body shaft through a central shaft hole of the wheel body, a snap spring groove is formed at the one end part of the wheel body shaft, and a snap spring is arranged on the snap spring groove. The wheel structure has the advantages of ensuring labor-saving operation, facilitating mounting and maintenance, facilitating manufacturing, saving materials and prolonging service life.