The invention discloses a fast assembly device for a plastic profiled material sizing mould. The fast assembly device for the plastic profiled material sizing mould comprises a base and a pressing plate. The pressing plate is located on the base and connected with the base. The base and the pressing plate are both mounted at the side surface of a steel bottom plate of the sizing mould. An circular-arc-shaped bump is arranged at the lower side of the pressing plate and an circular-arc-shaped groove, which is matched with the circular-arc-shaped bump, is arranged at the joint of the base and the circular-arc-shaped bump. The pressing plate and the base are further connected by screws. Two screw holes are formed in the side part, which is connected with the steel bottom plate of the sizing mould, of the base. The base and the steel bottom plate of the sizing mould are connected in the way that the screws penetrate the screw holes. A groove-shaped block is arranged at one side, which is connected with the steel bottom plate of the sizing mould, of the pressing plate and a groove hole, which is matched with the groove-shaped block, is arranged at the corresponding joint of the steel bottom plate of the sizing mould. The device is simple in structure, convenient to manufacture, capable of assisting the installation of the parts of the plastic profiled material sizing mould skillfully, accurate in positioning, good in rapidness and convenience and high in position restoring accuracy.