Soil amendment with biochar is evaluated globally as a method to improve soil fertility and to mitigate climate change. However,the effects of biochar on soil biota have received much less attention than its effects on soil chemical properties. To investigate the effects of biochar on the amounts of different functional bacteria related to the nitrogen transformation and available nitrogen contents,two controls were adopted including the one was the only black soil with no fertilizer and biochar,the other was black soil plus fertilizers with no biochar. Biochar made by maize straw at 450℃ insulated from oxygen were applied to black soil with the same amount of fertilizer in a weight proportion of 1%,5% and 10% in present study,respectively. The results were as follows:the amounts of nitrogen-fixing bacteria,ammonifying bacteria and nitrifying bacteria in soybean rhizosphere were increased at the filling stage and the mature stage with 1% biochar application. The amount of nitrogen-fixing bacteria,ammonifying bacteria and nitrifying bacteria in soybean rhizosphere were increased in all growth stages except that the amount of ammonifying bacteria at the flowering stage was no remarkable effects with 5% biochar application. Significant differences were not observed of the amounts of nitrogen-fixing bacteria,ammonifying bacteria and nitrifying bacteria in soybean rhizosphere with 10% biochar application. Moreover,the amount of ammonium nitrogen was influenced with biochar application at the seedling stage,flowering stage and podding stage;the amount of nitrate nitrogen of soybean rhizosphere was increased at the flowering stage while decreased at the maturity stage with biochar application.