The invention relates to an ultra thin-walled automotive wire which comprises a conductor, a fixing layer coating on the surface of the conductor and an insulating layer coating on the surface of the fixing layer. The insulating layer is prepared from, by weight, 100 parts of PVC resin with a high polymerization degree, 20-40 parts of modified resin, 10-30 parts of plasticizer with a high molecular weight, 20-50 parts of flame retardant, 10-20 parts of nano-silicon dioxide, 5-20 parts of nano calcium carbonate and 0.5-8 parts of N-substituted maleimide heat-resistant modifier. According to the ultra thin-walled automotive wire, the safety of the wire is improved by means of the fixing layer and the insulating layer; by means of reasonable compatibility of the components of the insulating layer material and the synergistic effect of all the components, the prepared ultra thin-walled automotive wire has a good low temperature property and a high temperature-resistant grade, wherein the low-temperature impact brittleness temperature can reach -50 DEG C, and the ultra thin-walled automotive wire can be used for a long time at 125 DEG C; the ultra thin-walled automotive wire has an excellent mechanical property and excellent abrasion resistance, and therefore the service life of the wire is guaranteed.