A facile approach for the first synthesis of ocimarin,naturally occurring coumarins,was developed by employing a cerium(Ⅲ) chloride heptahydrate-catalyzed Pechmann condensation of phenols andβ-keto esters in a solvent-free system as key step,by which ocimarin was achieved by three steps starting from acetylacetic ether and resorcinol with total yield 23.2%.All structures of new compounds were confirmed by IR,~1H NMR and MS. A facile approach for the first synthesis of ocimarin, naturally occurring coumarins, was developed by employing a cerium (III) chloride heptahydrate-catalyzed Pechmann condensation of phenols and β-keto esters in a solvent-free system as key step, by which ocimarin was achieved by three steps starting from acetylacetic ether and resorcinol with total yield 23.2%. All structures of new compounds were confirmed by IR, ~ 1H NMR and MS.