The invention discloses a preparation method of a multifunctional polylactic acid fiber and belongs to the technical field of preparation of functional materials and functional fibers. The preparation method comprises 1, feeding functional metal ions into alpha-ZrP to obtain functional alpha-ZrP through ion exchange, then modifying the functional alpha-ZrP through KH550, carrying out acidification treatment on a carbon material to obtain an acidified carbon material, modifying the acidified carbon material through an E51 epoxy modifier to obtain a modified carbon material, and adding the KH550-modified functional alpha-ZrP into the modified carbon material to obtain a multifunctional nanocluster, and 2, carrying out blending granulation on the multifunctional nanocluster and a polylactic acid matrix, carrying out drying, and spinning the multifunctional polylactic acid fiber through a melt spinning method. The multifunctional polylactic acid fiber has the advantages of small antibacterial guest component content, uniform dispersion, lasting effects and simple operation.