A new cephalosporin derivate, cefazolin phthalidyl ester(CFZ-PT) was synthesized to improve oral absorption and bioavailability of parent drug by esterification of sodium cefazolin(CFZ). Partition coefficient studies showed that CFZ-PR is more lipophilic than CFZ. The pharmacokinetic characteristics of CFZ-PT and CFZ preparations were compared following oral administrations of these compounds to rabbits. The analysis of CFZ in plasma was conducted by HPLC method. The ester compound was not detected in plasma following oral administration of CFZ-PT was increased by yielding 3.5-fold bioavailability rather than CFZ. From the results of this experiment, it was concluded that CFZ-PT could be a novel prodrug of CFZ which can improve the oral bioavailability of CFZ.