The invention provides a method for producing gamma-polyglutamic acid by using Flammulina velutipes waste, and relates to the agricultural technology and the technical field of fungal solid culture material reuse. According to the present invention, Bacillus subtilis is inoculated in Flammulina velutipes waste, such that common feeds or live bacteria feeds can be produced, and the effective component gamma-polyglutamic acid (gamma-PGA) can be produced, wherein gamma-polyglutamic acid (gamma-PGA) is a novel environmentally-friendly biomaterial, has characteristics of no harm to the environment,edibility, no toxicity, no environment pollution, excellent biodegradability, excellent film forming property, excellent fiber formation, excellent plasticity, excellent adhesion, excellent moistureretention and other unique physicochemical and biological characteristics, and is the environmentally-friendly biological product, the large-scale extraction of gamma-polyglutamic acid (gamma-PGA) through the Flammulina velutipes waste is not reported, and the functional material gamma-polyglutamic acid (gamma-PGA) is favored by people, is gradually used in pharmaceutical manufacturing, food processing, and anti-freezing and preservation of vegetables, fruits and seafood, and can further be used in cosmetics industry, tobacco, leather manufacturing, plant seed protection and other fields; andwith the method, the new method for the bio-utilization of Flammulina velutipes waste is expanded, and the method has great development value and broad prospect.