The invention discloses a preparation method of high-light-resistance low-cost titanium dioxide. The method comprises the following steps: S1, simultaneously adding waste titanium oxychloride and phosphoric acid or phosphate into titanium dioxide-based material slurry, and homogenizing; s2, continuing to add phosphoric acid or phosphate, homogenizing, then adding a coating agent a, homogenizing, finally adding magnesium salt, and homogenizing; and s3, adjusting the pH value of the slurry to 7.5-8.5, then adding alkaline aluminum salt and waste titanium oxychloride at the same time, keeping the parallel flow pH value to 7.5-8.5, and homogenizing. The surface of the titanium dioxide is uniformly coated with the titanium phosphate, the titanium phosphate has good adhesive force, the titanium phosphate adheres to the surface of the titanium dioxide, oxygen is prevented from making contact with the surface of the titanium dioxide, and therefore the light resistance of the product can be improved; then the titanium dioxide is coated with a magnesium phosphate film layer, so that the light resistance of the titanium dioxide can be further improved; the outermost layer is coated with an aluminum oxide film layer, so that the dispersity and covering power of the titanium dioxide are further improved; and the production cost is effectively saved by replacing a conventional titanium source and a pH regulator with waste titanium oxychloride.