LaInO3 (LIO) represents a new, to the best of knowledge, type of perovskite oxides for deep-ultraviolet (DUV) photodetection owing to the wide bandgap nature (∼5.0 eV) and the higher tolerance of defect engineering for tunable carrier transport. Here we fabricate fast-response DUV photodetectors based on epitaxial LIO thin films and demonstrate an effective strategy for balancing the photodetector performance using the oxygen growth pressure as a simple control parameter. Increasing the oxygen pressure is effective to suppress the oxygen vacancy formation in LIO, which is beneficial to suppress the dark current and enhance the response speed. The optimized LIO photodetector achieves a fast rise/fall time of 20 ms/73 ms, a low dark current of 2.0 × 10-12 A, a photo-to-dark current ratio of 1.2 × 103, and a detectivity of 6 × 1012 Jones.