This invention relates to a preparation of ultraviolet light stability agent, its characteristic is that after 1-20 weight shares of nanometer TiO2 particle that surface modified by coupling agent and 40-60 weight shares of emulsifying agent solution of which density is 0.5-3wt% are mixed uniformly, disperse 3-10 minutes in supersonic wave(frequency: 19-21KHz,power: 50-250W), then the mixed liquor is added into three-necked bottle that has agitator, thermometer and reflux condenset, it is protected by nitrogen gas, add 5-10 weight shares of initiator solution of which density is 0.5-3wt% when the temperature is 50-80DEG C, continuously dropwise 10-54 weight shares of acrylics monomer, after monomer has been dropwised they react 1-2 hours, reduce the temperature to release materials, filter, obtain ultraviolet light stabilizer-polyacrylic ester/ complex particle of nanometer TiO2 by drying. This ultraviolet light stabilizer and giant molecule material are mixed, ageing effect is accelerated by ultraviolet light, the test result indicates that it raises the bearing ultraviolet light stabilizer of this giant molecule material, meanwhile it raises mechanic function.