The invention relates to lactobacillus casei-containing fermented oyster powder. The preparation method comprises the following steps of: homogenating oyster and water according to a ratio, adding protease according to the ratio, uniformly stirring, hydrolyzing, performing enzyme deactivation, cooling, centrifuging, taking supernatant, adding activated carbon according to the mass percent of the enzymatic hydrolysate, keeping the temperature to be 30-40 DEG C, filtering by using kieselguhr, and obtaining clarified oyster enzymatic hydrolysate; and inoculating probiotics according to the volume percent of the enzymatic hydrolysate, fermenting at the temperature of 35-40 DEG C for 6-8 hours, fermenting at the temperature of 4 DEG C for 2-4 days, and performing freeze drying on the fermentation liquor to obtain the fermented oyster powder. According to the product production process, the modern biotechnology and freeze drying technology are adopted, and the nutritional ingredients of the oyster are totally converted in the lactic acid fermentation process, so that the fermented oyster powder contains the active ingredients such as amino acids, glycogen, taurine, zinc and selenium in the nutritional ingredients of the oyster and also contains active lactobacillus casei, and the nutrition and health care functions are guaranteed.