Abstract: Cancer is a big threat to human health. Along with the understanding of the mechanisms of cancer progression and microenvironment, it has become very urgent to develop novel diagnostic and therapeutic strategies beyond conventional surgery, radiotherapy and chemotherapy. Compared with small molecule chemical and monoclonal antibody drugs, peptides are quite unique to act not only as hormones and inhibitors, but also as peptide vaccines to activate antitumor immune response. They could also be developed as molecular diagnostic tools. This review focuses on the recent progress of the mechanism of anti-tumor peptide, peptide optimization, targeting peptides and self-assembly, and future directions of anti-tumor peptides.