The disclosure discloses Bacillus subtilis for producing N-acetylneuraminic acid and application thereof, and belongs to the field of genetic engineering. The disclosure optimizes the expression levels of key enzymes in N-acetylneuraminic acid synthesis pathways on genome through promoters of different strength, reduces the protein synthesis pressure caused by the expression of enzymes on cells, and further integrates the three N-acetylneuraminic acids in a same Bacillus subtilis engineering strain. Bacillus subtilis with improved N-acetylneuraminic acid production is obtained, and the production reaches 10.4 g/L at the shake flask level, laying a foundation for further improving the NeuAc production from Bacillus subtilis.