Abstract: In this research,an acid purple soil deficient in Mo was used for pot experiment.Three strains of celB-labeled Bradyrhizobium celB3-5、celB3-7、celB4-5 were selected to inoculate Tianfu 9 peanut.Root nodule formed by gene marker strains would have color reaction with the test reagent.This characteristic can be used to detect effect of Mo and its application rate on the effectiveness and competitiveness of the peanut-Bradyrhizobium symbiosis.Results show that in the acid purple soil Mo deficit,single application of Mo,single inoculation of Bradyrhizobium or combination of the two all could promote symbiotic nitrogen-fixation and competitive ability of peanut-Bradyrhizobium in nodulation,(among) which the effect of combination was the best,followed by inoculation and single Mo application.The effect of application of 0.4% NH4MoO3 solution was more pronounced than that of 0.2% NH4MoO3 solution when applied alone,whereas the effect of the former was less pronounced than that of the latter when combined with inoculation.In terms of effectiveness and competitiveness,Strain celB4-5 took the best and followed with celB37 and celB3-5.