The invention discloses a method for fermenting 
food industry leftovers by using a 
fermentation agent containing 
bacillus velezensis, which comprises the following steps: (1) inoculating 
bacillus velezensis XDY021 bacterial liquid into a sterilized culture medium, carrying out shake-flask culture, and then transferring into a seed tank for culture to obtain the 
fermentation agent containing 
bacillus velezensis; (2) taking a 
fermentation substrate composed of 
protein-containing leftovers and 
sugar-containing leftovers, adding water, and 
grinding into 
slurry; and (3) putting the pasty fermentation substrate into a fermentation tank, adjusting the pH value, adding a fermentation agent containing bacillus velezensis, and fermenting for 24-120 hours, thereby obtaining the product. According to the method disclosed by the invention, the 
protein-containing leftovers and the 
sugar-containing leftovers are fermented by the fermentation agent containing bacillus velezensis, the particle size, the 
water insoluble content and the like of the obtained fermentation material just meet the requirements for culturing the spider, and the fermentation material is beneficial to 
ingestion of the spider and is particularly suitable for being used as a bait for culturing the spider. In addition, the bacillus velezensis XDY021 still exists, so that the bacillus velezensis XDY021 is resistant to storage, other infectious microbes cannot be bred in the storage process, and the phenomena of 
flatulence, expansion and the like cannot occur.