An improved synthetic method of saquinavir, an HIV protease inhibitor, is described. In comparison with the methods in the reported works, the improved procedures had several advantages, such as less expensive agents, shorter reaction time, and a smaller amount of the solvent needed. To measure the optical purities of the products, the intermediates were determined by means of chiral HPLC. Some of the intermediates can also be used for the preparation of new protease inhibitors. An improved synthetic method of saquinavir, an HIV protease inhibitor, is described. In comparison with the methods in the reported works, the improved procedures had several advantages, such as less expensive agents, shorter reaction time, and a smaller amount of the solvent needed To measure the optical purities of the products, the intermediates were determined by means of chiral HPLC. Some of the intermediates can also be used for the preparation of new protease inhibitors.