The utility mode provides a bracket of a semi-trailer cat ladder. The bracket is a rectangular frame arranged at the lower side of a semi-trailer goose neck, wherein, one long edge of the rectangular frame is connected with a lower wing plate of a vertical beam by a hinge, the two short edges of the rectangular frame are welded with fixed iron at the end far away from a hinge connecting edge, the fixed iron is detachablely and movably connected with a wing support or a perforating beam by bolts, the rectangular frame and the lower part of the goose neck form a space for receiving the semi-trailer cat ladder. The bracket structure of the utility model is simple and has convenient operation, does not occupy the trailer space, is particularly suitable for the semi-trailer such as a side curtain van vehicle, a sedan and an exhibition car, effectively solves the problem of the storage of the cat ladder and is very practical.