The invention discloses a method for removing porcelain by hydrofluoric acid and co-producing white carbon black, comprising the following steps: (1) immersing cast iron enamel defective products in a reaction vessel with hydrofluoric acid water solution, carrying out the heating reaction, generating silicon tetrafluoride gas, filtering, re-inputting filtrate into the reaction vessel, washing other substances by sodium hydroxide water solution, recovering cast iron and further processing waste residues; (2) using ammonia water to simultaneously absorb the silicon tetrafluoride gas and hydrogen fluoride gas, using ammonium fluoride water solution to absorb the silicon tetrafluoride gas which is not absorbed and heating, thereby obtaining ammonium fluosilicate solution; (3) using ammonia water to regulate pH for reaction, generating sediment, filtering, separating, acidifying a filter cake by sulfuric acid, aging, filtering, washing by water and drying, thereby obtaining the white carbon black. The recovery rate can be more than 90 percent by using the method to process the cast iron enamels, and the method has the advantages of short reaction time, reasonable utilization of the acid, high utilization rate of raw materials and low production cost.