A lipase-catalyzed enantioselective hydrolysis process under continuous in situ racemization of substrate by using trioctylamine as an organic base was developed for the production of (S)-naproxen from racemic naproxen thioesters in isooctane. Naproxen 2,2,2-trifluoroethyl thioester and 45 degrees C were selected as the best substrate and temperature, respectively, by comparing the time-course variations for the racemization of (S)naproxen thioesters containing an electron-withdrawing group. A detailed investigation of the effect of trioctylamine concentration on the kinetic behaviors of the thioester in racemization and enzymatic reaction was conducted, in which more than 70% conversion of the racemate (or 67.2% yield of (S)-naproxen) with ee, value higher than 92% was obtained.