The invention discloses a long-acting brightening agent and a preparation method thereof, and belongs to the technical field of surface treating agents. The long-acting brightening agent is prepared from, in weight percent, 10-20% of cetyl alcohol ester, 3-5% of nano-silica, 5-10% of nano-titania, 10-20% of sodium heavy alkyl benzene sulfonate, 5-10% of dinonyl naphthalene sulfonic acid, 0.1-3% ofemulsifiers, 0.1-1% of essence and the balance deionized water, and the sum of all raw materials is 100%. The preparation method of the long-acting brightening agent includes the steps: uniformly mixing the deionized water and the emulsifiers and then heating the deionized water and the emulsifiers to reach the temperature of 40-50 DEG C; adding nano-silica, nano-titania, sodium heavy alkyl benzene sulfonate and dinonyl naphthalene sulfonic acid; performing stirring for 10-60 minutes; separately adding cetyl alcohol ester; reducing the temperature to room temperature after uniform stirring; adding the essence and performing stirring for 1-3 hours to obtain the brightening agent. The brightening agent can be kept bright for a long time, cannot be easily contaminated by dust and is safe andenvironmentally friendly.