The invention relates to the technical field of semiconductor optoelectronic devices, in particular to a novel homojunction PIN ultraviolet detector comprising a substrate, a buffer layer, an N type ohmic contact layer, an absorption layer, a P type gradient doping layer, an N type ohmic contact electrode, and a P type ohmic contact electrode. The buffer layer is arranged on the substrate; the N type ohmic contact layer is arranged on the buffer layer; the absorption layer and the N type ohmic contact electrode are arranged on the N type ohmic contact layer; the N type ohmic contact electrodehas an annular shape and the absorption layer is arranged in the ring of the N type ohmic contact electrode; the P type gradient doping layer is arranged on the absorption layer; and the P type ohmiccontact electrode is arranged on the P type gradient doping layer. The working mode of the detector is as follows: light enters from the front end. The novel homojunction PIN ultraviolet detector hasthe following advantages: the electric field distribution is adjusted by the P type gradient doping layer, so that the collection efficiency of photo-generated carriers of the P type gradient doping layer is improved and thus the spectral response rate of the detector is increased.