The invention relates to a production method for preparing 2,5-dichloronitrobenzene (DCNB) through continuous nitration, which particularly realizes the recycling of waste acids in the preparing process. The invention provides a technological program capable of recycling acids for preparing 2,5-dichloronitrobenzene (DCNB) through the continuous nitration, which is characterized in that sulfuric acid and nitric acid are prepared into a mixed acid, the mixed acid and paradichlorobenzene are simultaneously fed into a three-stages kettle (ring) type continuous reactor to carry out nitration reaction, a nitration reaction solution discharged form the third-stage kettle (ring) type continuous reactor is stood for layering so as to obtain a nitrifying oil layer and a nitrifying waste acid, and the nitrifying oil layer is subjected to alkali cleaning, water washing and light component removal so as to obtain a 2,5-DCNB finished product; paradichlorobenzene is added into the nitrifying waste acid to extract organic matters in the acid layer, residual HNO3 in the acid layer is consumed, after the extraction is completed, the obtained product is layered so as to obtain an extraction oil layer and an extracted residual waste acid, the extraction oil layer is used for next-batch nitrification, the extracted residual waste acid after being concentrated and nitric acid are prepared into the waste acid for next-batch nitrification, a small amount of emulsion layer is produced in the process of recycling, and the emulsion layer after being combined with the nitrifying oil layer is subjected to alkali cleaning and water washing.