The invention discloses a method for preparing oxo-2,3-naphthyridine acetic acid with benzothiazole or other heterocyclic branched chains, the method comprising: making oxo-2,3-naphthyridine acetic acid Esters react with aniline derivatives. The invention also discloses a method for preparing such oxo-2,3-naphthyridine esters.