The invention provides an oxidizer used in the di-chlorine quinoline acid synthesis technology, which can effectively improve the problems that the time of the oxidation operation is long, the production capacity is limited, and the generated waste acid is not easy to be processed in the prior art. The oxidizer is oxyacid of chlorine, bromine and iodine and salts thereof, and peroxide. The invention further provides a novel method for synthesizing di-chlorine quinoline acid oxo by utilizing the novel oxidizer.