The invention discloses high-speed SNSPD with a high-absorption structure and a preparation method of the high-speed SNSPD. The SNSPD is based on a high-refraction-index incident medium and an air cavity structure, and can further improve the photon absorption rate of superconducting nanowire, and compared with the prior art, the SNSPD can achieves approximate 100 percent absorption rate with lower duty ratio in the condition of nanowire made of superconducting ultrathin membrane made of the same material and having the same thickness, so that the difficulty in electron beam lithography steps is greatly lowered, the SNSPD is beneficial to the preparation of superfine nanowire, the high-quality growth of superconducting films can be guaranteed through the adoption of an SOI substrate, the intrinsic quantum efficiency of a detector is not affected; moreover, the highest counting rate of the detector can be enhanced as the total length of the required nanowire is obviously reduced in the condition that the same effective detection area is guaranteed, and the probability of defect occurrence during the preparation process is obviously reduced.