AIM: To build up the structure of human fibrinogen receptor GPⅡb-Ⅲa, subsequently combined with its antagonist decorsin, and to investigate the interaction between decorsin and its receptor GPⅡb-Ⅲa at the molecular level.METHODS: A three-dimensional (3D) molecular model of human fibrinogen receptor GPⅡb-Ⅲa was generated by InsightⅡ, a distance geometry-based homologous modeling package. The structure of human fibrinogen receptor GPⅡb-Ⅲa was built by the InsightⅡ/Homology module using the corresponding of integrin alphaVbeta3 (PDB filecode 1JV2) as the template. Then the primary structures were optimized by energy minimization. Subsequently the structural model was docked with its antagonist decorsin (PDB filecode ldec). RESULTS: A good substratereceptor interaction model was achieved. The interaction sites with decorsin converge at domain 8 (βA domain of β3 subunit) of GPⅡb-Ⅲa. The direct interatomic contacts were made between 16 GPⅡb/Ⅲa residues and 10 decorsin amino-acid residues. These included van der Waals contacts, electrostatic interaction, hydrogen bond,and salt bridge. Residues in contact were concentrated in four dispersed regions of human GPⅡb-Ⅲa: the RGD reaction motif (118-132 of GPⅢa), the span from 210 to 213 of GPⅢa, Thr182 residue and Asp251 residue of GPⅢa; and they were distributed over five segments of decorsin: Aspl0 residue, Asnl8 and Lysl9 residues, Arg28 residue, RGD motif, and Asp35-Pro36-Tyr37 segment. CONCLUSION: This complex model plays an important role in development and research of some new drugs, especially a new guided fusion-type fibrinogen receptor antagonist.