Provided is a preparation method of a multifunctional polyamide fiber, and belongs to the technical field of functional materials and functional fiber preparation. The preparation method comprises the following steps that step1, functional metal ions are put in an alpha-ZrP through ion exchange to form a functional alpha-ZrP, and then using a KH550 modified functional alpha-ZrP, a carbon material is treated with acidification to obtain an acidified carbon material, an E51 epoxy modifier is used for modifying the carbon material after acidification, a modified carbon material is obtained, and the functional alpha-ZrP modified by the KH550 is added to the modified carbon material to form multifunctional nanoclusters; step 2, the multifunctional nanoclusters and a polyamide matrix are mixed and granulated at 180-270 DEG C, after being dried, and a multifunctional polyamide fiber is prepared by melt spinning. The addition of an antibacterial object component in the multifunctional polyamide fiber is few, the dispersion is even, the function is durable, and the operation is simple.