The invention discloses an aluminum silicon lanthanum boron quaternary intermediate alloy and a preparing method of the alloy. The aluminum silicon lanthanum boron quaternary intermediate alloy can be used for casting a refined aluminum silicon alloy. Industrial pure aluminum, silicon metal, an Al-10La intermediate alloy and an Al-3B intermediate alloy are taken as a raw material, the mass ratio of the four raw materials is 1:(0.2-0.4):(0.5-0.8):(0.8-1.2), a lanthanum boron compound in the aluminum silicon lanthanum boron quaternary intermediate alloy is evenly divided by eutectic silicon, no obvious agglomeration phenomenon exists, primary aluminum grains in the cast aluminum silicon alloy with the complex component are efficiently refined, particularly, in the high-silicon alloy, the excellent refining effect is obtained, the poisoning effect generated between the high-silicon alloy and metamorphic strontium cannot be generated, and therefore the comprehensive mechanical performance of the cast aluminum alloy is improved, and the casting performance of the aluminum alloy is improved. In addition, a refining agent has hardly any induction period, the refining effect is long in duration time, meanwhile, raw materials are rich, the cost is low, atmosphere protection is not needed, and a preparing device and a preparing technology are simple.