RS17 is a synthetically designed antitumor peptide that specifically binds to the CD47 molecule, inhibiting the interaction between CD47 and its ligand SIRPα on the macrophage surface membrane. The primary regulatory mechanism of RS17 involves blocking the transmission of the selective phagocytosis signal from CD47 to SIRPα, preventing macrophages from identifying tumor cells as self, and instead treating them as foreign substances for phagocytosis, thereby inhibiting tumor cell immune evasion. RS17 is applicable in studies of antitumor responses and immune evasion mechanisms.