The invention discloses a preparing method of titanium-rare earth composite adsorbent capable of efficiently removing arsenic, which can remove trivalent arsenic or pentavalent arsenic in water. Titanium salt and rare-earth salt serve as raw materials with the mole ratio of 1:4-10:1; in the presence of macromolecular organic substance, the raw materials are heated at the temperature of 60-100 DEGC until total hydrolysis; then, pH of solution is adjusted to be natural to generate precipitate; the precipitate is washed with water and dried at the temperature of 50-120 DEG C to constant weight;the adsorption quantity of pentavalent arsenic is above three times than that of traditional activated aluminium oxide, and the adsorption quantity of trivalent arsenic is above 10 times than that ofactivated aluminium oxide; the titanium-rare earth composite adsorbent has the characteristics of high adsorption volume, wide pH applicable range, stable performance, easy regeneration and the like and has favourable application prospect in removing arsenic of drinking water.