NOVELTY - A modified titanium dioxide powder comprises surface modified copper oxide quantum dot, where the crystal particle surface of the titanium dioxide powder is distributed with at least one of cuprous oxide and copper oxide by the quantum dot, and the high dispersion refers to that the mean size of the quantum dot is 1-100 nm.    USE - As photocatalyst for degrading optionally substituted phenols, aromatic, inorganic sulfide and organic sulfide contaminants, or for detecting the photo-electric conversion efficiency and for preparing the solar battery apparatus.    ADVANTAGE - The method for modifying titanium dioxide surface utilizes cuprous chloride saturated solution deposition method which is featured with low toxicity, high environmental protection, high selectivity and energy saving. As the cuprous chloride is sparingly soluble in water, the modification of micro cuprous oxide on the surface of the titanium dioxide is controlled, and the isopropanol is used as the dispersing agent so that the titanium dioxide is scattered uniformly.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of modified titanium dioxide powder involving adding excessive amount of cuprous chloride powder to the ultra pure water at room temperature, for being dispersed and stirred magnetically to obtain a saturated cuprous chloride suspension; filtering the saturated cuprous chloride suspension for fetching the clean liquid, and sealing and storing the saturated cuprous chloride solution in dark place, while the undissolved cuprous chloride is recycled for preparing the saturated cuprous chloride solution repeatedly; burning the titanium dioxide powder at 200-800 degrees C for 3 hours, then adding it to the isopropanol at room temperature for being dispersed ultrasonically so as to obtain the titanium dioxide-isopropanol suspension; added the saturated cuprous chloride solution to the titanium dioxide-isopropanol suspension under the magnetic stirring; adding the resultant suspension with excessive amount of sodium hydroxide or potassium hydroxide solution for being reacted with the cuprous chloride fully so as to obtain the titanium dioxide suspension deposited with cuprous hydroxide precipitates on the surface, where the suspension is stirred continuously for 10-60 minutes; filtering the resultant the titanium dioxide suspension for fetching the filtering slag, and then washing until the surface of the filtering slag does not have sodium hydroxide or potassium hydroxide, heating at 50-100 degrees C, and drying the filtering slag so that the cuprous hydroxide is decomposed for generating cuprous oxide.