In this paper, Bi₂O₂Se/TiO₂ heterostructures different mass fractions were synthesized by one-step hydrothermal method and characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy, and the ultraviolet detector based on Bi₂O₂Se/TiO₂ heterojunction was prepared. The experimental results show that the photodetection performance of Bi₂O₂Se/TiO₂ heterojunction detector is the best when the mass fraction of Bi₂O₂Se is 60% under 365 nm ultraviolet light. The photocurrent of Bi₂O₂Se/TiO₂ heterojunction is 7 times that of TiO₂ detector and higher than that of Bi₂O₂Se detector. The response time is about 30 ms, which is 1/6 of that of TiO₂ detector. The responsivity and detectivity are 10^-3 A/W and 1.08×10⁷ cm·Hz^1/2/W, respectively, which are also one order of magnitude higher than that of TiO₂ detector. This is mainly because the heterojunction formed by the combination of Bi₂O₂Se and TiO₂ promotes the separation of photogenerated electrons and holes.