The invention discloses a method for preparing 1-tert-butyl-3-(2,6-diisopropyl-4-phenoxyphenyl) thiourea, comprising the following steps: a, 4-phenoxy- 2,6-Diisopropylaniline and its salts react with carbon disulfide and an organic or inorganic base in a solvent to generate the corresponding 4-phenoxy-2,6-diisopropylanilino dithiomethane acid salt; b, 4-phenoxy-2,6-diisopropylphenylamino dithiocarboxylate reacts with tert-butylamine in organic solvent to generate 1-tert-butyl-3-(2,6-dithiocarboxylate) isopropyl-4-phenoxyphenyl)thiourea. The preparation method provided by the invention has the advantages of few reaction steps, high total yield, simple operation, mild reaction conditions, cheap and readily available raw materials, and suitability for industrial production.