Poly γ-glutamic acid (γ-PGA) is a kind of water soluble and biodegradable polymer, which is nontoxic toward humans and the environment. Therefore, the potential applications of γ-PGA and its derivatives have been of interest in a broad range such as food, cosmetics, medicine, water treatment and agriculture. This paper summarizes γ-PGA synthesis pathways in microorganisms, producing strains, fermentation parameters, as well as separation and purification methods. In addition, the prospect of γ-PGA application on agriculture was introduced, pointing out the problems and the future trends in research and application of γ-PGA.