L-valine is an essential amino acid.It is applied in food field.L-valine is mainly produced by microbial fermentation.High yielding strain is the foundation of the fermentation industry.Brevibacterium flavum FP-01 was mutated by atomspheric and room temperature plasma,ultra violet,diethyl sulfate,and nitrosoguanidine to breed mutants overproducing L-valine.A high yielding mutant strain,B.flavum FP-6-56,was obtained.It was resistant to amino acid structural analogues and was amino acid auxotrophic.54.5 g/L of L-valine was produced by the mutant strain in shaking flask.The results of genetic stability tests indicated that the genetic marker and L-valine production of B.flavum FP-6-56 were highly stable.A high-yield L-valine mutant strain with high genetic stability was obtained by mutation breeding.