Belonging to the technical field of bioengineering, the invention discloses a bacillus subtilis for efficient exogenous protein expression and high density culture. According to the invention, a screening and separation method is employed to acquire a bacillus subtilis with high protein expression quantity, and the six genes srfC, spoIIAC, amyE, nprE, aprE and bamA are knocked out to obtain B. subtilis WS5 with a preservation number of CCTCC M 2016536. The bacillus subtilis WS5 is adopted as the expression host for construction of a beta-CGTase genetically engineered bacterium. The beta-CGTase genetically engineered bacterium is subjected to 3L fermentor culture, foams produced in the fermentation process are obviously decreased, a mirror does not detect spore production, almost no extracellular amylase and protease exist in the culture process, after 70h of fermentation culture, the beta-CGTase enzyme activity reaches 270U/ml, and DCW reaches 70g/L.