Thymosin α 1 was synthesized manually. The washing condition and the test of the degree of coupling were studied. In addition, the analytical method of crude product was set up. Thymosin α 1 was synthesized with the solid-phase method, by using the base-liable Fmoc group to protect the α-amino acid and N,N′-diisopropylcarbodiimide (DIC) as the coupling regent. The crude product was analyzed by reversed-phase high performance liquid chromatography, SDS-PAGE and liquid chromatography/mass spectroscopy.The synthesis yield was 84.89%. The analytical results indicated that the crude product contained much thymosin α 1, and the purity was 50.3%. DIC solid-phase chemical synthesis of thymosin α 1 was applicable, and the yield was improved greatly compared to other known methods.