The invention discloses bacillus subtilis. According to the bacillus subtilis, the category name is bacillus subtilis PG-8, the bacillus subtilis is collected at China general microbiological culture collection center (CGMCC), the registered number is CGMCC NO. 6324, and the collection data is 10, July, 2012. The invention further discloses application of the bacillus subtilis in preparation of gamma-D-polyglutamic acid. The bacillus subtilis is cultured in a culture medium containing L-glutamic acid only, and then, the gamma-D-polyglutamic acid of 30-60 g / L can be accumulated under optimized conditions. According to the bacillus subtilis, a variety of carbon and nitrogen sources can be utilized, culture conditions are extensive, the operation is convenient and simple, the yield of the gamma-D-polyglutamic acid is high, and the production cost is low, so that the bacillus subtilis can be widely applied to the fields of plant water conservation, food additives and the like.