The invention discloses a bacillus cereus, and preparation and application of the bacillus cereus. A bacillus cereus strain Aj080319IA-16 is separated from an intestinal tract of a wild stichopus japonicus selenka and collected in China Center for Type Culture Collection (CCTCC) along with a collection number of CCTCC M 2010315. The screened bacillus cereus has remarkable antagonistic action on pathogenic bacteria of a sea cucumber, and has the effects of increasing the growth speed, immunity and intestinal digestive enzyme activity of the stichopus japonicus selenka. The screened bacillus cereus is safe and non-toxic for the sea cucumber, fast in breeding speed, easy to culture and strong in adaptability on environment, and is capable of being bred quickly to form predominant bacteria. The researched and developed microbiological preparation is simple and convenient to use and operate and only needs to be added into a feed for feeding, so that the preparation is suitable for young stichopus japonicus selenka breeding and disease control in a variety of stichopus japonicus selenka breeding processes. By means of the preparation, the use of antibiotics can be reduced or replaced, and an important role is played in reducing chemical residues, improving the product quality of the sea cucumber and guaranteeing the food safety.