Bacillus subtilis is an attractive host for the production of heterologous secretory proteins for several reasons: it is non-pathogenic and capable of secreting functional extracellular proteins directly to the culture medium, a great deal of vital information concerning genetic manipulation and large-scale fermentation has now been acquired. This paper summarized the characteristics of gene expression, expressing vectors, the technology of the expression of heterologous protions and some limitations of secretory expression in Bacillus subtilis.