A TiO2/NPB heterogeneous one-directional nanorod array ultraviolet detector based on a self-exhausting effect and a preparation method thereof belong to the field of ultraviolet detection technology. The detector is composed of an FTO glass substrate, an optical sensing layer TiO2/NPB heterogeneous one-directional nanorod array and Au electrodes, wherein the optical sensing layer TiO2/NPB heterogeneous one-directional nanorod array is composed of a TiO2 one-dimensional nanorod array which vertically grows on the surface of the FTO, and an NPB material which is filled in the gaps between clearances of the TiO2 one-dimensional nanorod array. After a P-type NPB material is filled in an N-type TiO2 one-dimensional nanorod array, in a data state, a P-N heterogeneous material generates a self-exhausting effect and a built-in electric field and an exhausting area are formed; carrier concentration of the material is reduced, and the detector is in a high-resistance state so that dark current of the detector is effectively reduced. On the condition of ultraviolet ray radiation, photon-generated carriers are separated and accumulated for narrowing an exhaust region until the exhaust region disappears, and the self-exhausting effect of the device is counteracted, thereby ensuring relatively high gain and relatively large optical current of the detector.