The invention discloses a silicon-based photoelectric detector for photoelectric monolithic integration and a preparation method thereof, which relates to a silicon-based photoelectric monolithic integrated circuit. The invention provides the silicon-based photoelectric detector which is completely compatible with the commercial BCD standard technology and is used for photoelectric monolithic integration, and provides the preparation method thereof. The silicon-based photoelectric detector is provided with a P type silicon substrate, a BN+ epitaxial layer, a BP+ epitaxial layer, an N-EPI epitaxial layer, an N-well layer, a P-well layer, a P+ layer, an N+ layer, an Al layer, a field oxide layer, SiO2 insulating medium layers and a Si3N4 surface passivation layer, wherein the P type silicon substrate, the BN+ epitaxial layer, the BP+ epitaxial layer, the N-EPI epitaxial layer, the N-well layer, the P-well layer, the P+ layer and the N+ layer are arranged on the same silicon wafer; the field oxide layer is a silicon oxide layer generated on the surface of the silicon wafer; a metallic aluminum layer is deposited on the surface of the silicon wafer; three SiO2 insulating medium layers are attached to the silicon substrate from bottom to top according to the preparation sequence through the deposition technology; and the Si3N4 surface passivation layer is attached to the SiO2 insulating medium layers through the deposition technology.