Objective Eucheuma is rich in nutrients and can be an important raw material of food after processed. This study was designed to establish a feasible method of purifying polypeptides from eucheuma and investigate their activity against platelet aggre?gation and bacterial growth. Methods We extracted peptides from eucheuma with acidic solution, detected the effects of different doses of small molecular polypeptide ( 0, 5, 10, 20, and 40μg/mL) on the growth of Escherichia coli ( D1314) and Staphylococcus aureus (s.agr+, RN4220) using the method of turbidity, and analyzed the anti?platelet aggregation activity of the peptides with a whole blood aggregometer. Results The rates of peptides extracted from 50, 100,150, and 200 g of eucheuma were 0.382%, 0.405%, 0.389%, and 0.389%, respectively. The purified sample exhibited a single band on SDS?PAGE. The relative molecular weight of the peptides was about 3kD. The extracted peptides inhibited the growth of Escherichia coli, Staphylococcus aureus, and thrombin?induced platelet aggregation in a dose?dependent manner, with inhibition rates of 44.71%, 51.86%, and 75.00%, respectively. Conclusion The present method can be used to successfully purify low?molecular?weight peptides from eucheuma and effectively inhibit platelet aggre?gation and bacterial growth. The peptides extracted is a potential anti?platelet aggregation agent.