Mesorhizobium huakuii tpp mutant HKtpp was obtained by homologous recombination,and the effects of mutant HKtpp on the growth and symbiotic nitrogen fixation function of the strain were studied by autogenous growth and plant pot experiment. The results showed that the mutant HKtpp reduced the strain growth,and the activity of glutathione reductase in the mutant strain was significantly decreased. The mutant HKtpp formed effective red nodules,but its nitrogenase activity was decreased by 26.4%. It is indicated that tpp gene played an important role in the growth and symbiotic nitrogen fixation of Rhizobium.