A photoassisted O-2 annealing method is proposed to anneal (Ba0.75Sr0.25)TiO3 thin films grown by rf magnetron sputtering,. A deuterium lamp, which emits strong ultraviolet and vacuum ultraviolet light, was used as the light source of our photoassisted O-2 annealing system. It was found that we could achieve a leakage current density lower than 3 x 10(-8) A/cm(2) at 2 V and a dielectric constant, epsilon, as high as 158.6 by annealing (Ba0.75Sr0.25)TiO3 thin films in this system at 650degreesC for 2 h.