The present disclosure discloses a folding ladder and a top tray thereof. The top tray comprises a fixed plate and a movable plate. The movable plate is disposed on a rear side of the fixed plate and is rotatably connected to the fixed plate, and the movable plate is configured to be rotated to switch between an unfolded position and a folded position. When the movable plate is in the unfolded position, the movable plate is horizontally arranged side-by-side with the fixed plate, and a rear surface of the fixed plate abuts a front surface of the movable plate to maintain the movable plate in a horizontal position and to resist a downward force of gravity. When the movable plate is subjected to an upward pushing force and is rotated to be folded into the folded position, the movable plate abuts the rear side of the fixed plate.