The invention provides a 
superconducting nanowire single photon detector based on a deep 
silicon etching process and a preparation method. The 
detector comprises an SOI base which is composed of a back substrate, a buried 
oxygen layer and top 
silicon in sequence from bottom to top, a first anti-reflection layer which is disposed on the surface of the top 
silicon, a second anti-reflection layer which is disposed on the surface of the back substrate, a deep groove which penetrates through the second anti-reflection layer, the back substrate and the buried 
oxygen layer, an 
optical cavity structure which is disposed on the surface of the first anti-reflection layer, superconducting nanowires which are disposed between the first anti-reflection layer and the 
optical cavity structure, and a mirror which is disposed on the surface of the 
optical cavity structure. By 
etching the deep groove on the substrate, the distance between a 
coupling optical fiber and the device is narrowed, the use of a long-focus lens in the traditional back-
coupling superconducting nanowire single photon detector is avoided, and alignment 
coupling between the MU head of an 
optical fiber and the device is facilitated. The problem concerning long-distance focusing in the optical cavity structure and the influence of the Fabry-Perot cavity of the susbtrate on the 
absorption efficiency are avoided. The 
absorption efficiency of target 
wavelength is improved. The detection efficiency of the device is improved.