The utility model belongs to a packing box, in particular to a packing box with automatic back sealing. Most of the existing packaging boxes are of the folding-wing type or bottom-buckling type. When folding the folding-wing packaging box, the four side wings connected to the bottom of the box are first folded into a mouth shape, and then the two side wings are crossed and overlapped, and then the box surface is folded to make it established. square. When folding the bottom box, first fold the four sides of the box into a mouth shape, then fold the tabs on the bottom of the box, and then fold the box surface to make it square.