This technical achievement solves the problem of stable discharge of tail water in refractory pharmaceutical parks, including enhanced pretreatment technologies for ozone oxidation and hydrolytic acidification of tail water in the park, and co-treatment technology for pretreated tail water and domestic sewage. The COD of biologically treated wastewater in the pharmaceutical park reaches the 300mg/L standard. However, it still contains a large amount of refractory organic substances such as p-methyl phenol, dimethyl phthalate, acetophenone, etc., with BOD/COD<0.1. Poor biodegradability. After comparison of process technologies, ozone oxidation, hydrolytic acidification and their combination processes were selected to carry out enhanced pretreatment of the tail water of the pharmaceutical park. After a small scale and a pilot test of 10 tons/day, the key parameters were obtained as follows: ozone dosing of 20~30 mg/L, hydrolytic acidification time of 6~9 hours, BOD/COD can be increased to above 0.3; The pretreated pharmaceutical wastewater and domestic sewage with a COD of 500mg/L are co-treated through the A2O process, and the proportion of pharmaceutical wastewater is controlled to be 20%~30%. Using the principle of biological co-metabolism, the effluent can stably reach the first-class urban sewage A emission standard. The above process technologies have been applied and demonstrated in the construction project of Shenyang Western Sewage Treatment Plant in the middle reaches of Hun River. The scale is 70,000 tons/day of tail water in the pharmaceutical park and 180,000 tons/day of domestic sewage. The comprehensive treatment cost per ton of water is about 1.15 yuan. The treatment of tail water in the industrial park provides a replicable technology and model, with significant environmental, economic and social benefits.