An electro-absorption modulator, comprising: a substrate layer, comprising a silicon substrate and an oxide layer disposed on the silicon substrate; top-layer silicon, wherein a waveguide layer is formed on the top-layer silicon; a doping layer, formed on the top-layer silicon, wherein the doping layer comprises a first doping panel and a second doping panel, a first-type light doping area is formed on the first doping panel, a second-type light doping area is formed on the second doping panel, the first-type light doping area and the second-type light doping area are located on two sides of the waveguide layer and closely abut against the waveguide layer, and the first-type light doping area, the waveguide layer, and the second-type light doping area form a PIN junction; and a modulation layer, disposed on the waveguide layer and connected in parallel to the PIN junction, wherein a beam with a specific wavelength propagates along the waveguide layer, enters a modulation area formed by the modulation layer and the waveguide layer, and then propagates between the modulation layer and the waveguide layer in an oscillation manner; and when a modulating electrical signal is reversely applied to the first-type light doping area and the second-type light doping area, a light absorption coefficient of the modulation layer for the beam changes with the modulating electrical signal, and after the beam passes through the modulation area, optical power of the beam also correspondingly changes, so that electro-optic modulation is implemented for the beam; wherein the modulation layer is made by mixing germanium with silicon according to a pre-determined proportion; wherein the modulation layer is grown by using a selective epitaxial area, and the selective epitaxial area is obtained by etching; and a length and a thickness of the modulation layer are determined by the selective epitaxial area, so that the length and a width of the modulation layer meet two waveguide modes: a horizontal single mode and a vertical single mode. a substrate layer, comprising a silicon substrate and an oxide layer disposed on the silicon substrate; top-layer silicon, wherein a waveguide layer is formed on the top-layer silicon; a doping layer, formed on the top-layer silicon, wherein the doping layer comprises a first doping panel and a second doping panel, a first-type light doping area is formed on the first doping panel, a second-type light doping area is formed on the second doping panel, the first-type light doping area and the second-type light doping area are located on two sides of the waveguide layer and closely abut against the waveguide layer, and the first-type light doping area, the waveguide layer, and the second-type light doping area form a PIN junction; and a modulation layer, disposed on the waveguide layer and connected in parallel to the PIN junction, wherein a beam with a specific wavelength propagates along the waveguide layer, enters a modulation area formed by the modulation layer and the waveguide layer, and then propagates between the modulation layer and the waveguide layer in an oscillation manner; and when a modulating electrical signal is reversely applied to the first-type light doping area and the second-type light doping area, a light absorption coefficient of the modulation layer for the beam changes with the modulating electrical signal, and after the beam passes through the modulation area, optical power of the beam also correspondingly changes, so that electro-optic modulation is implemented for the beam; wherein the modulation layer is made by mixing germanium with silicon according to a pre-determined proportion; wherein the modulation layer is grown by using a selective epitaxial area, and the selective epitaxial area is obtained by etching; and a length and a thickness of the modulation layer are determined by the selective epitaxial area, so that the length and a width of the modulation layer meet two waveguide modes: a horizontal single mode and a vertical single mode.