The invention relates to the field of medicaments, in particular to an integrin blocking agent HM-3 which has the function of inhibiting tumor angiogenesis, integrin affinity and a bonding capacity and application thereof. The blocking agent is a polypeptide modified with polyethylene glycol, and the modified integrin blocking agent polypeptide can be applied to treatment of solid tumors. During application of the integrin blocking agent to preparation of a tumor treatment medicament, the sequence and structure of the integrin blocking agent is mPEG-SC20k-Ile-Val-Arg-Arg-Ala-Asp-Arg-Ala-Ala-Val-Pro-Gly-Gly-Gly-Gly-Arg-Gly-Asp. The integrin blocking agent polypeptide designed in the invention is scientific, reasonable, practical and effective, can be used for preparing a treatment medicament for treating human solid tumors, and has remarkable social value and market value; and the treatment spectrum of the integrin blocking agent is expanded greatly, and novel thought and prospect are provided for future development of medicaments.