The invention discloses a novel aluminium-coated steel conductor automobile electric wire and a preparation method thereof. The aluminium-coated steel conductor automobile electric wire comprises a conductor body; the conductor is formed by aluminum and steel in a rolling and extruding manner; the conductor body has a solid square section; the body is 2.8-11mm in length of side of the section; theouter surface of the body is coated with an insulating layer; the insulating layer has a hollow square section; and the insulating layer is 4.9-17.5mm in length of side of the section. Compared withthe conventional aluminium-coated steel conductor electric wire with a stranded structure, the aluminium-coated steel conductor automobile electric wire provided by the embodiment can save 5-10% of the conductor material under the same rated carrying capacity; in addition, the breaking elongation rate is far higher than that of the conventional copper stranded conductor and the novel aluminum stranded conductor; the aluminium-coated steel conductor cable with a square section has the advantage of compact structure; and the overall dimension is reduced by about 18-25% compared with that of theconventional stranded aluminium-coated steel conductor cable.