A process for preparing high-purity ferrous Qiongate by burning slag, which involves the integrated reaction of acid dissolution and reduction of hematite slag with ultrafine hematite and industrial sulfuric acid to obtain ferrous sulfate slurry. The slurry is then dissolved and filtered to obtain an acid resistant ferrous solution, followed by concentration, refrigeration, crystallization, and centrifugal separation of the ferrous sulfate solution to obtain a high-purity ferrous sulfate product - heptahydrate ferrous sulfate product. This heptahydrate ferrous sulfate can be directly used for the preparation of high-grade iron oxide series pigments. Most of the finished mother liquor is sent to the reaction kettle to recover the active ingredients such as free acid repellent, acid repellent iron, and ferrous sulfate. The purity of ferrous sulfate produced by the present invention is greater than 99.0%, the consumption of sulfuric acid is low, and the purity of ferrous sulfate heptahydrate produced is high. It can be directly used for the preparation of iron oxide series pigments, simplifying the process of using ferrous sulfate to prepare iron oxide series pigments