The invention relates to a method for preparing high-tenacity low-elongation polyamide 6 fibers. The method for preparing high-tenacity low-elongation polyamide 6 fibers comprises the following steps of: 1) fusion: sliding pre-dried polyamide 6 and performing fusion to obtain spinning solution; 2) spinning: performing spinning by enabling the spinning solution to enter a spinning component, wherein monofilaments are sprayed out from a spinneret plate; 3) bundling and oiling: bundling the monofilaments reaching a bundling and oiling point and oiling the surface of a bundle, wherein spinning oil contains polyamide chain extender and ultraviolet screening agent; 4)hot drawing: enabling oiled bundle to sequentially pass through No.1 combined rollers, No.2 combined rollers and No.3 combined rollers to perform hot drawing; 5) winding: enabling the bundle after hot drawing to pass through a separate interlacer and winding at a winding head to obtain high-tenacity low-elongation polyamide 6 fibers. The polyamide 6 fibers prepared by adopting the method disclosed by the invention has the characteristics of high tenacity and low elongation, the addition of functional additives does not influence the spinnability and fiber performance of the spinning solution, and the sunlight resistance, high temperature resistance and oxidation aging resistance of the fibers can be effectively improved.