The invention discloses a method for producing sodium aluminate crystal by utilizing a low-grade aluminium-containing raw material. The method comprises the following steps of (1) mixing sodium ferrite, low-grade bauxite and lime to prepare materials to be leached; (2) mixing and leaching caustic alkali liquor and the materials to be leached, filtering to obtain a leaching slag and a leaching solution; (3) carrying out refined filtration on the leaching solution to obtain refined-filtration filtering cakes and sodium aluminate refined solution; (4) evaporating and concentrating the sodium aluminate refined solution till the concentration of NaOH is 400-450g/L, cooling and crystallizing, drying a filtered solid phase to remove water, and obtaining the sodium aluminate crystal. The method disclosed by the invention has the beneficial effects that a closed circulation of a new process for producing the sodium aluminate crystal by utilizing the low-grade aluminium-containing raw material is formed, and the effects of changing wastes into valuables and having no pollutant emission are realized.