Mechanical and antibacterial properties of polylactid acid have to be improved for advanced applications of medical instruments, artificial tissues and active packaging, etc. In this work, antibacterial polylactid acid nanocomposites are developed by using silver-graphene oxide hybrid (Ag@GO) as filler via in-situ polymerization and direct mechanical blending method, respectively. The effects of Ag@GO content and preparation method on the mechanical and antibacterial properties of the polylactid acid nanocomposites are investigated. It is shown that the flexural strength of the Ag@GO/polylactid acid nanocomposites increases from 326 to 942 K Pa as the Ag@GO content increases from 0 to 2.0 wt.%; the antibacterial rate (to Escherichia coli ATCC 25,922 and Staphylococcus aureus ATCC 6538) increases from 0 to 99% as the Ag@GO content increases to 2.0 wt.%. Further, the flexural strength and antibacterial properties of the composites prepared by the in-situ polymerization method are greatly improved and are consistently higher than those of the composite counterparts prepared by the direct mechanical blending method.