The invention provides a polypeptide or a pharmaceutically acceptable salt thereof and application of the polypeptide or the pharmaceutically acceptable salt in preparation of a tumor multidrug resistance reversal agent, and belongs to the technical field of biological medicines. The polypeptide can selectively act on
tumor cells with negatively charged
cell membranes through
electrostatic interaction, has small influence on normal cells, and has good selectivity; meanwhile, a hydrophobic fragment in the structure is inserted into a
tumor cell membrane phospholipid skeleton to destroy the integrity of a
cell membrane, change the permeability of the
cell membrane and inhibit the
membrane protein function, so that more anti-tumor
drug molecules can be promoted to enter
tumor cells, the accumulation of the
drug in the
tumor cells is improved, the function of ABC
transport protein on the membrane can be influenced, and the anti-tumor effect is improved. The
excretion of
intracellular drugs is inhibited, and finally, the aim of reversing the multidrug resistance of tumors is fulfilled. Therefore, the polypeptide or the pharmaceutically acceptable salt thereof can be used as a novel
peptide tumor multidrug resistance reversal agent, can be potentially used in anti-tumor
clinical treatment, and has a wide development prospect.