Abstract: To apply copper alginate fibers in medical as a new alginate fiber, copper alginate fiber was researched and evaluated against Escherichia coli (E.coli) and Staphylococcus aureus (S.aureus), using antibacterial zone and flash shaking method, and analyzed anti-bacterial mechanism by the scanning electron microscopy (SEM). The result showed that copper alginate fibers had antibacterial effects, the antibacterial rate was 97.4% against E.coli, 66.2% against S.aureus; SEM images indicated that bacteria obviously changed after contacting with fibers, the main reason was that copper ion had a damaging effect on pericellular and cell wall. Furthermore, bacterial osmotic pressure was changed and protein synthesis were impeded, and then the normal metabolism of bacteria was destroyed, and finally, bacteria died.