1. A waterproof card holder, comprising:a card holder frame;
a cover plate located at a top of the card holder frame;
a sleeve integrated with and extending from an inner side of the cover plate, including a through-hole penetrating through the sleeve and the cover plate, wherein the sleeve comprises a sleeve body, a first opening and a second opening, the first opening and the second opening being disposed at two ends of the sleeve body, respectively; and
a waterproof mechanism accommodated in the sleeve, wherein the waterproof mechanism comprises a first end portion limited to be inside the sleeve, a second end portion having an outer diameter smaller than that of the first end portion, and a waterproof ring sleeved on a periphery of the first end portion, wherein the waterproof ring and the sleeve form a sliding sealing structure therebetween, the first end portion is limited to be only movable within a stroke between the first opening and the second opening, and the second end portion is capable of passing through the first opening to be in contact with a card retracting mechanism;
wherein the first opening has an inner diameter smaller than an outer diameter of the first end portion; a first blocking slope is formed at a junction between the first end portion and the second end portion; and a second blocking slope, corresponding to and cooperating with the first blocking slope, is formed on a side of the first opening facing the second opening; and
wherein the sleeve has an axis, the through hole is aligned with the axis, and the first blocking slope and the second blocking slope are each at an oblique angle relative to the axis.