The invention relates to a clean production process of a dicamba synthesis midbody, and provides a clean production method of 2,5-dichlorophenol. The clean production process comprises the following steps: stirring 30-70% of dilute sulfuric acid and 2,5-dichloroaniline in a backflow state for 1-2hours, wherein the weight ratio of the dilute sulfuric acid to the 2,5-dichloroaniline is (6:1)-(9:1); after the reaction, cooling the reaction liquid to 0-5 DEG C, and dropping 10-60% nitroso-sulfuric acid and stirring for 2 hours to obtain diazonium liquid, wherein the molar ratio of the 2,5-dichloroaniline to the nitroso-sulfuric acid is 1:(1.0-1.5); carrying out pyrohydrolysis on the synthesized diazonium liquid at 140-170 DEG C to obtain 2,5-dichlorophenol; and carrying out diazotization synthesis on part of the hydrolyzed dilute sulfuric acid subjected to recovery processing as batch charging of dilute sulfuric acid, and synthesizing the other part of the dilute sulfuric with SO2 to be 10-60% nitroso-sulfuric acid, and then applying to diazotization synthesis. According to the synthesis process, no waste salt or phenolic wastewater are generated during diazotization reaction, the reaction yield is as high as 95%, and diazonium liquid is subjected to pyrohydrolysis and the dilute sulfuric acid can be recycled, so that the cycle use of the two can be achieved. The clean production process belongs to a clean and environment-friendly production process.