The invention relates to a peptide compound and its pharmaceutical composition for inhibiting platelet aggregation and preventing/treating thrombogenic diseases. The invention develops pentapeptides and hexapeptides derived from snake venom C-type lectin-like proteins (CLPs) fragments, which can inhibit platelet aggregation and have antithrombotic activity without hemorrhagic tendency. Accordingly, they can be used as potential agents for the prevention and therapy of thrombogenic diseases.