The invention discloses a nanometer particular bismuth-loaded titanium dioxide based composite photocatalytic material and a preparation method and application thereof, and belongs to the technical fields of functional nano-material preparation, solar energy utilization and environmental protection. According to the composite photocatalytic material, a titanium dioxide semiconductor nano-material responsive to sunshine is taken as a substrate and is modified with a bismuth nano-material which has photogenerated hole capture ability. Through photogenerated hole capture, photogenerated electrons are effectively separated from holes to improve the photocatalytic reduction efficiency of a material system. The photocatalytic reduction material can be directly applied to photocatalytic reduction purification of carcinogenic anions (such as nitrate and bromated) in water under sunlight, and the problem that a traditional photocatalytic material is low in reduction efficiency is solved.