The invention discloses a synergistic treatment device for dust removing and desulphurization. The synergistic treatment device adopts the structure that a primary smoke dust removing and desulphurization area, a secondary smoke dust removing and desulphurization area and a defogging device are sequentially arranged in a tower body in the smoke flowing direction; a porous distribution plate of the primary smoke dust removing and desulphurization area is arranged in the tower body above a smoke inlet; primary spraying layers are arranged in the tower body above the porous distribution plate; a synergistic ring I is arranged between two adjacent primary spraying layers; a liquid collection disc of the secondary smoke dust removing and desulphurization area is positioned in the center of the tower body above the primary spraying layer; a ring-shaped plate is arranged in the tower body above the liquid collection disc; the inner diameter of the ring-shaped plate is smaller than the outer diameter of the liquid collection disc; secondary spraying layers are fixed above the ring-shaped plate in the tower body; a synergistic ring II is arranged between two adjacent secondary spraying layers. The synergistic treatment device has the advantages that dust removing and desulphurization are subjected to hierarchical and synergistic treatment, and a desulphurization spraying tower can be used for achieving efficient dust removing and desulphurization simultaneously, so that the investment and the operation cost can be reduced.