The invention relates to a dampproof polyester insulating rope for hot-line work and a preparing method thereof and belongs to the technical field of development and preparation of insulating ropes for hot-line work. The insulating rope comprises a dyed core material, a transition layer evenly covering the dyed core material, and a waterproof agent layer evenly covering the transition layer, wherein the waterproof agent layer is a perfluorocarbon-6 waterproof agent and/or perfluorocarbon-4 waterproof agent. The preparing method comprises the steps of conducting doubling and twisting on polyester filament yarn to obtain wires, conducing dyeing on the wires, taking the wires out, washing and drying the wires, treating the wires with water-based macromolecule negative ion emulsion with the particle size of 5-200 nanometers and a coupling agent through impregnation so as to achieve negative ionizing of the fiber surface, conducting impregnation positive ion waterproof treatment and high-temperature baking, and finally obtaining the rope. The dampproof insulating property of the rope is far higher than that of the prior art. The rope is especially suitable for hot-line work in a high-humidity environment, storage and transportation can be achieved more easily, and using is safer.