The invention discloses antibacterial polyester composite fiber. The composite fiber takes polylactic acid fiber as a core wire, the polylactic acid fiber is coated with polyester fiber, wherein the polylactic acid fiber comprises 95-98 parts by weight of polylactic acid particles and 2-5 parts of a modifier, the modifier comprises the following components in parts by weight: 70-80 parts of silveroxide, 10-15 parts of zinc oxide, 2-5 parts of polytetrafluoroethylene, 3-5 parts of calcium carbonate and 1-2 parts of molybdenum phosphate, the polyester fiber comprises 93-95 parts by weight of polyester and 5-7 parts by weight of an antibacterial agent, wherein the antibacterial agent comprises 40-50 parts by weight of zinc-loaded calcium phosphate, 20-25 parts of silver and copper-loaded calcium phosphate, 10-15 parts of isothiazolinone, 15-20 parts of a chinese herbal medicine extracting solution and 5-10 parts of a titanate coupling agent. The polylactic acid fiber is added into the polyester fiber, so that the prepared polyester composite fiber is comfortable in hand feeling, high in strength and certain in antibacterial property.