Abstract: The present disclosure relates to the technical field of microorganisms and fermentation, and specifically discloses a Lactobacillus acidipiscis, a fermented soymilk, and a preparation method and use thereof. Lactobacillus acidipiscis HAU-FR7 is disclosed with a deposit number of CGMCC NO. 19253. The Lactobacillus acidipiscis HAU-FR7 is a facultative anaerobe that can reduce soy isoflavones, and the Lactobacillus acidipiscis HAU-FR7 can not only grow under aerobic conditions, but also convert daidzin and genistin distributed in the soymilk into DHD and DHG under aerobic conditions. Moreover, the Lactobacillus acidipiscis HAU-FR7 has stable conversion capacity, and solves the problem of shortage of facultative anaerobes in the research and development of soy functional foods. The DPPH radical-scavenging capacity of DHD and DHG is significantly higher than that of daidzein and genistein.