The invention discloses a preparation method for etravirine. The method comprises the following steps: performing nucleophilic substitution on a pyrimidine ring to generate an intermediate IV under the action of an alkali by taking a compound II and a compound III as initial raw materials; performing the nucleophilic substitution on the intermediate IV and aminobenzonitrile under an alkaline condition to generate a key intermediate V; performing ammoniation on the key intermediate V in a microwave reactor to generate an intermediate VI; performing bromination on the intermediate VI to generate a target product, namely the etravirine I. The preparation method disclosed by the invention is high in reaction selectivity and easy to operate; compared with the original synthetic method, the reaction time is greatly shortened; the energy consumption is reduced; the reaction yield is improved; the overall yield reaches 38.5 percent; the preparation method is suitable for industrial large-scale production.