The invention discloses a chlorination process waste acid resource reutilization method which comprises the following steps: S1, firstly neutralizing chlorination process waste acid, and controlling the
neutralization pH value to be 2.5-3.5; s2, then adding
iron oxide black seed crystals; s3, carrying out oxidation treatment on the
system added with the
seed crystal, further neutralizing the
system, and controlling the
neutralization pH to generate large-particle-size
iron black; and S4, carrying out separation to separate the large-particle-size
iron black from other precipitates so as to obtain an
iron black product. The waste acid is neutralized firstly, the pH of the waste acid is increased, and
iron oxide black is prevented from being dissolved again during subsequent
iron oxide black seed crystal. And then iron black
crystal seeds are added, so that
ferric hydroxide which is neutralized and separated out during subsequent oxidation treatment is promoted to be converted into large-particle-size iron black crystals, the particle size of the iron black crystals is obviously larger than that of precipitates of other
metal ions, the iron black crystals can be effectively separated from the other precipitates, and the purity of the iron black product is greatly improved.