The invention relates to a 
tumor targeting polypeptide and a preparation method thereof. The 
amino acid sequential structure of the polypeptide of the invention is CFPVPGHDLVC. The preparation method comprises the following steps: co-culturing a pC89 phage 
peptide library for expressing 108 
protein polypeptides with different sequences and 
human breast cancer cell strain MDA-MB-231 repeatedly for many times; screening phages which express specific polypeptides and can penetrate a 
cell membrane and enter 
cytoplasm and / or 
nucleus, amplifying the phages 
in vitro and carrying out 
DNA sequencing, and deducing exogenous 
amino acid sequences inserted on the phages; co-culturing the screened specific polypeptide phages, other 
human tumor cells and normal cells 
in vitro, and detecting the specificity of 
cell tumor of the polypeptide phages; and according to the polypeptide sequences and the detecting result of the cell specificity, artificially synthesizing the 
tumor targeting polypeptide. The invention has potential clinical application values for specific vectors of 
breast cancer targeting 
gene therapy, and also provides powerful 
technical support for screening polypeptides with affinity and specificity of other types of malignant tumor cell strains in the future. In addition, the polypeptide of the invention contains only 9-11 
amino acid residues, can be synthesized easily, and has relatively small spatial position change, easy 
quality control of the polypeptide and convenient use.