The invention discloses polyferric sulfate as well as a preparation method and a preparation device of the polyferric sulfate. The preparation method comprises the following steps: conveying the following components into a mixing tank in percentage by weight: 40 percent to 50 percent of iron sulfate heptahydrate and 60 percent to 50 percent of titanium dioxide waste sulfuric acid, and blending the materials; adjusting the concentration range of the titanium dioxide waste sulfuric acid H2SO4 to be 21 percent to 23 percent to obtain mixed reaction materials; conveying the reaction materials into a reaction tower, and adding a sulfate composite rare-earth solution as a reaction cocatalyst when conveying the reaction materials into the reaction tower; controlling the temperature in the reaction tower to be 40 DEG C to 60 DEG C; after all the blended materials enter the reaction tower, adding a sodium nitrite solution as a reaction catalyst; continually introducing oxygen gas into the reaction tower so that the oxygen gas and the reaction materials make oxidization, hydrolysis and polymerization reactions under the action of the cocatalyst and the catalyst; after effectively converting Fe<2+> ions in the materials into Fe<3+> ions, obtaining liquid polyferric sulfate. With the adoption of the polyferric sulfate as well as the preparation method and the preparation device of the polyferric sulfate, the production efficiency can be greatly improved, environmental hazards are reduced, and a more prominent water purification and coagulation effect is realized.