The invention relates to a method for preparing a magnetic photocatalyst by use of waste toner. According to the method, the magnetism of the waste toner and a characteristic that a resin material on the surface of the toner has bonding property at certain temperature are utilized, TiO2 powder is uniformly bonded on the surface of the toner by a rotary heating method, and the TiO2 magnetic photocatalyst is prepared; the TiO2 magnetic photocatalyst is recovered and reutilized easily due to the magnetism of the toner, and SiO2 on the surface of the toner can prevent reduction of photo-catalytic activity caused by diffusion of transition metal ions. According to the method, high temperature treatment is not required, Fe3O4 in the toner is prevented from being converted into alpha-Fe2O3 to lose magnetism, and a phenomenon that the catalytic activity is reduced due to a situation that Fe<2+> diffused in TiO2 is converted into Fe<3+> during high temperature treatment is avoided. The method has simple process, the magnetic photocatalyst can be recycled, and while the waste resource utilization is realized, no secondary pollution is caused in the whole process.