The invention relates to the technical field of production technologies of polyglutamic acid, in particular to a technology for producing polyglutamic acid through fermentation of wastewater generatedin a Longkou bean vermicelli processing technology. The invention aims at recycling the wastewater generated in the bean vermicelli processing technology, and utilizing bacillus subtillis natto for fermenting the wastewater to produce the polyglutamic acid. In this way, the sewage treatment difficulty is lowered, and resources are also recycled; meanwhile, the production cost of the polyglutamicacid is lowered, and the application field and range of the polyglutamic acid are indirectly expanded.