With N-[(9H-Fluoren-9-ylmethoxy)carbonyl]-leucine ( Fmoc-Leu-OH ) and N-[(9H-Fluoren-9-ylmethoxy)carbonyl]-proline ( Fmoc-Pro-OH ) as starting materials, the classic Fmoc solid phase synthesis scheme for cyclopentapetide was employed. The linear peptapeptides were synthesized by protecting and deprotecting the amine using standard Fmoc solid phase peptide synthesis, including N-methylated amino acid. The cyclization step was completed using Benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate ( PyBOP ) as coupling reagent. Herein, two Galaxamide analogues G1 and G2 were synthesized and characterized by means of 1HNMR, 13CNMR, ESI-MS. Their anti-tumor activity in vitro were investigated through the MTT assay. The results demonstrated that proline-containing Galaxamide analogue G2 possess potent cytotoxicity on human breast cancer cell line MCF-7, which exhibited IC50 values of 5.85 mg /L.