The invention provides a lactobacillus buchneri and an application thereof in fermenting, converting and compounding high-value organic acid. The lactobacillus buchneri is named as GBS3 (Lactobacillus buchneri) and is collected in China Center for Type Culture Collection (CCTCC) with the collection number of CCTCC No.M 2016215. The strain provided by the invention is an original strain, and then phenyllactic acid and lactic acid are synchronously compounded through microbial fermentation metabolism; and the phenyllactic acid can be compounded through microbial conversion on the basis of taking the strain cell of the strain provided by the invention as a whole-cell catalyst and taking phenylpyruvic acid and glucose as substrates. The strain provided by the invention is separated from the traditional fermented food pickle, the biological safety is high, conversion reaction conditions are mild, and the conversion rate is high; the final concentration of lactic acid in the fermenting liquid can reach 1.8g/L, and the final concentration of phenyllactic acid can reach 13g/L; the concentration of phenyllactic acid in the fermenting liquid can reach 12g/L; and therefore, the industrial application prospect is extensive.