The utility model provides a trailer and a tool kit thereof. The tool kit of the trailer comprises a frame, a kit door and locking parts, wherein the frame comprises a front frame, a back frame, an upper frame, a lower frame, a left side frame and a right side frame, an opening is formed among the front frame, the lower frame, the left side frame and the right side frame, and a tool enters the frame via the opening; the kit door is located at the opening and comprises a lower kit door and an upper kit door, the lower kit door is connected with the lower frame through first pivoting parts in a pivoted manner, and the upper kit door is connected with the lower kit door through second pivoting parts in a pivoted manner; the locking parts are used for locking the kit door and the frame. According to the tool kit of the trailer, the kit door is divided into two or more small doors to be folded, so that the height of the kit door can be increased to the extent that an upper frame of the kit door is higher than accessories of the trailer, and opening and closing actions of the kit door are not affected by the accessories of the trailer. According to the tool kit of the trailer, the height and the size of the kit door of the tool kit are increased under the condition that the kit door does not interfere with the accessories of the trailer, such as a hook provided with a rope, a rope tensioner and the like.