Effective separation and fast transport of photogenerated carriers are vital links determining the photocatalytic performance. Heterostructure constructed by two complementary semiconductors is a feasible strategy to achieve this goal. By one‐pot hydrothermal method, 0D‐TiO2 nanoparticles are loaded onto 2D‐CuGaO2 nanosheets, forming a mixed dimension, closely combined heterostructure. The photocurrent density of CuGaO2/TiO2 heterostructure is ∼16.6 μA/cm2, which is 1.24 times higher than that of pristine CuGaO2 nanosheets (∼13.4 μA/cm2) and 15 times higher than that of TiO2 (∼1.1 μA/cm2). In the tetracycline hydrochloride degradation experiment, the degradation efficiency of tetracycline hydrochloride by CuGaO2/TiO2 heterostructure reached 99% within 90 min, which was 1.2 times the degradation efficiency of CuGaO2 nanoparticles (82%) and 20.2 times the degradation rate of TiO2 (4.9%). A series of experimental characterizations combined with density functional theory calculations revealed that it is the built‐in electric field in the CuGaO2/TiO2 interface region that drives the photogenerated electron–hole pairs to travel in the opposite direction, thus inhibiting their recombination. Furthermore, the energy band offset of the CuGaO2/TiO2 interface makes it easier for the photogenerated holes and electrons to gather onto the valence band of the CuGaO2 nanosheets and the conduction band of the TiO2 nanoparticles, respectively. Therefore, appropriate interface lattice matching, suitable configuration of band gap and band edge positions, and strong opposite drive of interface electric field enable CuGaO2/TiO2 heterostructure to achieve wide spectral response and effective separation of photogenerated electron–hole pairs at the same time.