The invention provides a method for treating dinitrobenzene wastewater generated by the nitration of benzene mixed acid, wherein the method comprises the following steps: (1) acidification; (2) iron-carbon reduction; (3) condensation; (4) flocculating sedimentation; and (5) general biochemical treatment of sedimentation water. When the dinitrobenzene wastewater generated by the nitration of benzene mixed acid is treated by the method, the contents of the matters of nitrobenzene, nitrophenol and the COD in the wastewater are greatly reduced; after further biochemical treatment, the wastewater can easily meet the water discharge standard; and compared with the prior treatment technique, the method has the advantages of low cost and good effect.