The potential application of a designed self-assembly peptide CH3CO-Pro-Thr-Phe-Cys-Phe-Lys-Phe-Glu-Pro-NH2 (named as P1) as a cartier of 5-Fluorouracil (5-Fu) for controlled release in vitro was studied.5-Fluorouracil (5-Fu) was selected as a representative anticancer drug due to its extensive use in treating digestive system cancer and breast cancer.The interaction between P1 and 5-Fu was detected by fluorescent quenching experiments and atomic force microscopy (AFM).The quenching mechanism of 5-Fu and P1 system was dynamic by performing fluorescent quenching experiments at different temperatures.The thermodynamic analysis demonstrated that the interaction between 5-Fu and P1 was hydrophobic interaction.The complexes prepared by the interaction between peptide and 5-Fu appeared as large granular particles of about 20 nm in height under AFM (denoted as5-Fu-P1),24 times larger than the original 5-Fu particles.According to the results,an interaction model was proposed.Furthermore,5-Fu-P1 complexes exhibited an efficient controlled release of 5-Fu in vitro.The research suggested that P 1 might be a candidate carrier for drug delivery,providing a substitution agent for 5-Fu.