The invention belongs to the technical field of edible fungi hereditary and genetic engineering, and particularly relates to grifola frondosa UDP-glucose pyrophosphorylase and application thereof. Through the genetic engineering technology, the UDP-glucose pyrophosphorylase gene is overexpressed or silenced in grifola frondosa, the quantity of mycelia in grifola frondosa recombinant bacteria and the yield of mycelia polysaccharides and exopolysaccharides can be significantly increased or reduced separately, and the composition of monosaccharide in the mycelia polysaccharides and exopolysaccharides of the grifola frondosa is significantly affected. The grifola frondosa UDP-glucose pyrophosphorylase provides a research basis for mastering a controlling mechanism for synthesis/metabolism of grifola frondosa polysaccharide and efficiently fermenting and producing a stable-quality polysaccharide product.