The invention discloses a multilayer film photodetector based on optical singular point design and a detection method thereof. The multilayer film photodetector comprises a substrate and a multilayerfilm arranged on the substrate, wherein the substrate is an optical material with transparent communication wave band; and the multilayer film is provided with the optical singular point, and a one-dimensional periodic array is formed by alternately arranging lossless optical materials and lossy optical semiconductor materials, four layers of films are used as a structural unit. The real refractive index, imaginary refractive index and film thickness of the material are accurately regulated and controlled according to the characteristic matrix of light transmission in the multilayer film, so that a unidirectional non-reflection phenomenon that one side reflectivity is not zero and the other side reflectivity is theoretically zero occurs in the detector structure at a specific wavelength. When an external light source is incident on the detector, the refractive index of the semiconductor material changes due to the photoelectric effect, reflection appears at the non-reflective end, so that the purpose of detecting the external light source is achieved. The multilayer film photodetector based on the optical singular point design has the advantages of novel and intuitive detection technology, high sensitivity, good stability and low cost of required detection equipment.