The invention relates to a method for preparing a loaded nano TiO2 composite material by using precipitated white carbon black as a carrier. The method comprises the following steps of: adding water into the precipitated white carbon black to prepare slurry with stirring, adding acid to adjust the pH value, then cooling the slurry, and adding TiCl4 solution and ammonium sulfate solution in turn for reaction; heating the reaction solution to a certain temperature, adding ammonium carbonate solution to adjust the pH value of the solution, and then ageing the solution for certain time; and finally, filtering, washing, drying and calcining the reaction product to obtain the precipitated white carbon black loaded nano TiO2 composite material. The composite material has excellent photocatalysisperformance under ultraviolet light and visible light, and the degradation and removal rate of formaldehyde is more than 80 percent in 24 hours under a fluorescent lamp.