The invention concerns a cooling and molding water tank for a plastic complicated profile. A plurality of molding blocks and water collection plates are provided along the length inside the tank, and they are spaced each other. The advantage of this invention is that: the cooling water flows alternately in cycle or periphery-inner-periphery. It makes the complicated profile cool homogeneously and efficiently upon the high speed extrusion pulling and provides the profile with good molding effect and quality.