The invention provides a preparation method of conductive glass fibers. The method comprises the steps that alkali-free glass fibers are immersed in an aqueous hydrochloric acid solution, after immersing is completed, the immersed glass fibers are fully rinsed with water and dried, and hydroxylated glass fibers are obtained; the hydroxylated glass fibers are immersed in an aqueous polyethyleneimine solution, after immersing is completed, the immersed glass fibers are fully rinsed with water and dried, and glass fibers surface-modified with polyethyleneimine are obtained; the glass fibers surface-modified with polyethyleneimine are put into an aqueous copper sulfate pentahydrate solution, after immersing is conducted, an aqueous sodium thiosulfate solution is added, the immersed glass fibers are taken out after a reaction is conducted, rinsed with water and dried, and cuprous sulfide and glass fiber composite conductive fibers are obtained. The technology is adopted for preparing the conductive glass fibers, equipment used in the technology is low in investment cost, operation is easy, the reaction condition is mild, the applicability is high, the treatment effect is good, the fiber performance loss is low, the quality is reliable, environmental pollution can be reduced, and the method is suitable for industrial production.