This paper was aimed to breed manganese ion(Mn2+)-resistance and high citric acid-yielding strain with mutation,and analyze its characteristics.A high yielding-citric acid and Mn2+-resistance strain was screened by ultraviolet(UV) radiation and nitrosoguanidine(NTG) treatment.The influences of Mn2+ concentration on the specific activities of key enzymes and respiratory pathway were investigated in the mutant strain during the citric acid fermentation.The citric acid production of the mutant UV-141 increased by 92.4% when it was cultured with glucose as the sole carbon source in shake flask fermentation.Compared with culture without Mn2+,the citric acid production and the maximum ratio of consumption rate of the mutant UV-141 increased by 107% and 16.7,respectively.The maximum specific activity of aconitase decreased by 15.8%,while the specific activity of NAD+-(NADP+-) isocitrate dehydrogenase maintained at a low level,which was in favor of the accumulation of citric acid.In addition,Mn2+ could weaken the decrease of citric acid,which was caused by the inhibition of alternative respiratory chain(AOX) in presence of salicylhydroxamic acid(SHAM).The citric acid production of the mutant strains was obviously higher than that of the wild strain.For the mutant strain,Mn2+ could promote glucose metabolism,decrease the specific activity aconitase,and weaken the influence of the SHAM on AOX pathway,thus lead to the abundant accumulation of citric acid.