The invention belongs to the field of metal manufacturing, and discloses an automobile light chassis aluminum alloy structural member and a preparing method thereof. The automobile light chassis aluminum alloy structural member is prepared from titanium, lead, manganese, silicon, iron, copper, magnesium, zinc, chrome, nickel, tin and the balance aluminum. The automobile light chassis aluminum alloy structural member has few bubbles inside, is good in mechanical performance, high in strength and high in corrosion resistance and high temperature resistance, is good in stability when used as an automobile part and is worthy of popularization; the product defects that original thin-wall support products have stress concentration and are prone to cracking are overcome, toughness and ductility are high, and the ductility is far superior to that of an existing product; aluminum alloy components are strictly controlled, the content proportions of Mn and Mg are independently set, and thus mechanical performance is improved; and accordingly, the automobile light chassis aluminum alloy structural member has good market prospects.