The invention relates to crosslinked polyglutamic acid hydrogel and a preparation method thereof, wherein the crosslinked polyglutamic acid hydrogel is stable, uniform in dispersion and low in concentration. The preparation method comprises the following steps of firstly, adopting a high concentration crosslinking formula for preparing gamma-polyglutamic acid rubber blocks, then, adding a water-based solution for homogenizing and crushing the gamma-polyglutamic acid rubber blocks, and obtaining the crosslinked polyglutamic acid hydrogel which is stable, uniform in dispersion and low in concentration. The preparation method of the crosslinked polyglutamic acid hydrogel which is stable, uniform in dispersion and low in concentration is few in step, stable in product character and suitable for industrial production and application; by controlling the concentration of crosslinked polyglutamic acid in a product, series products with improved viscosity can be obtained, the products are prone to being hydrated so that the products can be uniformly applied to and dispersed on the skin surface, and no sticky or flaking phenomenon occurs to the skin surface.