The invention discloses a preparation method of an aluminum alloy material for polishing aluminum, which comprises the following steps: mixing Mg powder and Si powder, carrying out ball milling for 1-2 hours, adding reinforcing powder, and continuously carrying out ball milling to obtain Mg-Si composite powder and reduce the existence of free silicon; the Mg-Si composite powder after ball milling is smelted at the temperature of 800 DEG C, the primary phase content in the formed Mg-Si alloy is small, then Al powder is added to obtain an alloy system, the aluminum alloy material is prepared through the steps of adding an oxidation compensation agent, refining, slagging-off, degassing, standing, casting, homogenizing and the like, the element content of Mg and Si in the prepared aluminum alloy material is low, and the prepared aluminum alloy material is high in mechanical strength and good in mechanical property. The forming rate of intermediate alloy Mg2Si is reduced, the content of excessive Si can be greatly reduced, the ductility of the material is improved, the aluminum alloy material can be bent, extruded, stamped and other machining is facilitated, free silicon cannot be excessively separated out in the polishing process, the surface of the product is not damaged, the yield of the aluminum alloy polished product can be better improved, and the quality of the finished product is greatly improved.