Abstract: The present disclosure discloses a method for co-producing synthetical rutile and polymeric ferric sulfate with waste sulfuric acid, which includes the following steps of: S1, performing deep reduction on ilmenite to obtain reduced ilmenite with a metallization rate of 85% or more; S2, leaching the reduced ilmenite with waste sulfuric acid; S3, performing solid-liquid separation on a mixed solution after the leaching in step S2, and drying a solid to obtain synthetical rutile, wherein a filtrate is a ferrous sulfate solution; and then performing step S4 or S5 to obtain a polymeric ferric sulfate finished product.