Abstract: This paper was to design a cyclic RGD peptide tumor inhibitor with high affinity to integrin α_νβ₃ receptor by molecular docking technique. cRGD molecular library was built and an optimal structure of cRGD peptide with the lowest score that was Cys-Arg-Gly-Asp-(D)Ser-Cys was screened out using the function of DOCK procedure of the V-life software. Based on the moiety a dimer linked by Tyr-(D)Ser-Lys-(D)Ser-Ser and with a side chain Gly-Gly-(D)Ala-Gly on Lys was synthesisized and ⁹⁹Tc^m-cRGD dimer was prepared. Its radiolabeled efficiency, stability, water soluble and affinity in vitro were evaluated. Under the reaction condition of room temperature, 1 g/L SnCl₂•2H₂O and the 30 min of reaction time, labeling efficiency reachs （87.42±3.21）%. After Sephadex G10 purification, the radiochemical purity is no less than 95%. In both mediums of saline and fresh human serum, the radiochemical purity keeps high stability in room temperature and 37℃.Then the equilibrium dissociation constant（K_d） on U87 human glioma cells was determined. After the reconstruction of the cRGD dimer, it possesses higher water-soluble and affinity, octanol-water partition coefficient lg P value is -1.96±0.01 and K_d value is (0.089±0.052)×10^-9 mol/L. cRGD peptide screened by computer-aided drug design (CADD) system can bind to integrin α_νβ₃ specifically, and be a promising radiotracer for integrin α_νβ₃-positive tumors imaging.