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;
a waterproof mechanism accommodated in the sleeve, wherein the waterproof mechanism comprises a main body, a first end portion located inside the sleeve, a second end portion protruding from the sleeve, and waterproof rings located on a periphery of the main body and close to the first end portion, wherein each of the waterproof rings and the sleeve form a sliding sealing structure therebetween; and
a waterproof circle disposed on a periphery of the cover plate, wherein the waterproof circle and an inner side wall of a slot of a metal casing form a sealing structure therebetween,
in a direction along which the first end portion, the main body and the second end portion are arranged, the waterproof mechanism has a length smaller than a length of the sleeve; and
the waterproof rings comprise a first set of waterproof ring and a second set of waterproof ring that are separated from each other, wherein the second set of waterproof ring is closer to the second end portion than the first set of waterproof ring, each of the first set of waterproof ring and the second set of waterproof ring comprises at least one waterproof ring; and at anywhere between the second set of waterproof ring and the second end portion, a gap is formed between the main body and the sleeve.