The invention discloses a preparation method of a nano-doped polyamide parallel elastic composite fiber. According to the method, dry chips are molten and then accurately metered by metering pumps andextruded, and two extruded melts are conveyed into the same spinning box and composite component through pipelines, converged in a spinneret plate or at an outlet of the spinneret plate, trickled tobe cohered together, cooled and formed in a cross air blasting manner and post-treated to obtain the parallel composite fiber. According to the method, one or more of nano-layer silicate, metallic compounds and rare earth compounds are doped into polyamide in a melt blending or in-situ polymerization manner to adjust interaction between molecules of one component of the composite fiber, polyamideself-curling parallel composite fiber is prepared through a bi-component melt compound spinning and drafting integrated device by the aid of difference of shrinkage rate of a modified component and anunmodified component, and the method solves the problems of low strength, poor moisture absorption, intolerance to high temperature, high machine wash cost and the like of a current elastic fiber.