Thin_film one_dimensional photonic crystal omnidirectional reflector used in vis ible region can be achieved by using angle domain overlapping reflectance bands. By using this method, the relative band width of the omnidirectional reflector consisting of four TiO2/SiO2 thin_film photonic crystals i s up to 41 33%. By comparison, the relative band width of the omnidirectional reflector c onstructed under the same condition as the above is only 1426% by using the co nventional frequency domain overlapping. The basic principle of the angle domai n overlapping is described. A thin_film one_dimensional photonic crystal omnidir ectional reflector used in visible region is calculated and given. Meanwhile, th e omnidirectional reflector used in ultraviolet region can be constructed by usi ng this new method, which cannot be obtained by the conventional method.