γ-polyglutamic acid (γ-polyglutamic acid, referred to as γ-PGA) by L-glutamic acid through the formation of a γ-amide bond of poly amino acid compounds, is a microbial Bacillus subtilis fermentation to form water-soluble anionic polymer. It has excellent water solubility, super absorbability and biodegradability. The degradation product is pollution-free glutamic acid. It can be used as water retaining agent, heavy metal ion adsorbent, flocculant, sustained-release agent and drug carrier, etc. It is widely used in agricultural planting, soil treatment, environmental protection, food, medicine, cosmetics and other industries.