With Ag-loading MWNTs antibacterial agent as functional material, the antibacterial functional PET fibers were prepared by melt blending spinning-draft one-step method. The crystallinity and the orientation of specimens were characterized by differential scanning calorimetry, polarization microscope and sound velocimeter. Moreover, the mechanical properties and antibacterial properties were measured. The results showed that the antibacterial PET fibers had good spinnability when the content of Ag-loading MWNTs less than 1.0 % (wt); compared with pure PET fibers, the degree of crystallinity, the degree of orientation and the fracture strength were improved, but the elongation was decreased; the antibacterial PET fibers exhibited excellent antibacterial properties against E.coli by the method of flask shaking.