The invention relates to a method for treating boron-containing wastewater in a 6-hydroxyl-8-chloro ethyl caprylate preparation process. According to the method for treating boron-containing wastewater in a 6-oxo-8-chloro ethyl caprylate preparation process, tetrabutylammonium bromide is used as a catalyst, a 6-oxo-8-chloro ethyl caprylate dichloroethane solution and a potassium borohydride ammonia water solution are subjected to a mixed reaction, 6-hydroxyl-8-chloro ethyl caprylate is obtained from the organic layer after the reaction, and ammonia water is recovered by concentrating the layer; and the method for treating boron-containing wastewater comprises: 1, after recovering the ammonia water, adding a proper amount of water, and adding an inorganic acid in a dropwise manner to acidify until the pH value is 1-2; 2, precipitating boric acid solid, filtering, drying the solid, and recovering; 3, evaporating the filtered boric acid mother liquor to remove a proper amount of water, cooling to a temperature of less than 30 DEG C, precipitating a potassium salt solid, drying the solid, and recovering; and 4, applying the mother liquor obtained in the step 3.