Cyclobutane pyrimidine dimer (CPD) is the most abundant DNA photolesion, and it can be repaired by photolyases based on electron-transfer mechanisms. However, photolyase is absent in the human body and lacks stability for applications. Can one develop natural enzyme mimetics utilizing nanoparticles (termed nanozymes) to mimic photolyase in repairing DNA damage? Herein, we observe the successful reversal of thymine dimer T<>T to normal T base by TiO2 under UVA irradiation. Time-resolved spectroscopy provides direct evidence that the photogenerated electron of TiO2 transfers to T<>T, causing structural instability and initiating the repair process. T-T- would then undergo bond cleavage to form T and T-, and T- returns an electron to TiO2, finishing the photocatalytic cycle. For the first time, TiO2 is discovered to exhibit photocatalytic properties similar to those of natural enzymes, pointing to its extraordinary application potential as a nanozyme to mimic photolyase in repairing DNA damage.