The invention belongs to the field of non-ferrous metallurgy, and in particular relates to a method for producing metal aluminum or aluminum magnesium alloy from low grade bauxite. The technical scheme of the invention is as below: first acid leaching is carried out on the low grade bauxite for preparing aluminum chloride, and an electrolyte system comprises a flux, a solute and additives. The flux comprises 0-60 wt.% of NaCl, 25-75 wt.% of KCl and 0-66 wt.% of MgCl2; then the solute AlCl3 accounting for 5-50 wt.% of the flux, an additive LiCl accounting for 0-5 wt.% of the flux, an additive KF accounting for 0-5% of the flux, an additive MgF2 accounting for 0-5 wt.% of the flux or an additive AlF3 accounting for 0-5 wt.% are added, wherein the solute AlCl3 is added from the bottom of electrolytic bath; the interpolar voltage is controlled at 2.3-3.3 V, the cathode current density is at 0.5-1.5 A / cm<2>, and the electrolysis temperature is 450 -500 DEG C; in the process of electrolysis, the anode generates chlorine gas, which is recycled, and aluminum or aluminum alloy precipitates at the cathode. The method of the invention has low power consumption, low electrolytic temperature and low production cost, solves the problem of aluminum chloride evaporation and dendrite generation electrolysis, causes no environmental pollution, and is easy in equipment realization.