The invention discloses a method for extracting vanadium from a waste SCR denitration catalyst by taking iron salt as a roasting additive. The method comprises the following steps: 1) mixing materials: mixing the waste SCR denitration catalyst with the iron salt to obtain a mixed material; 2) roasting: roasting the mixed material to obtain roasted clinker; 3) reducing: mixing the roasted clinker,a reducing agent and water, adjusting the pH of slurry to be 0.8-1.5, carrying out a reduction reaction, and carrying out solid-liquid separation to obtain vanadium-containing leachate and residues; 4) adjusting the pH of the vanadium-containing leachate, and carrying out a vanadium precipitation reaction and solid-liquid separation to obtain vanadium precipitate; and 5) calcining the vanadium precipitate to obtain vanadium pentoxide. According to the method, the waste SCR denitration catalyst is recycled, and the emission of pollutants can be reduced.