The effects of different biochar application rates on soybean yield and the enzyme activity of rhizosphere soil were studied to provide reasonable biochar application rates for increasing soybean yield. Taking the local conventional fertilization as the control(CK)，the biochar treatments were 27 kg·hm-2(B1)，54 kg·hm-2(B2)，81 kg·hm-2(B3)and 108 kg·hm-2(B4)，respectively，and the biochar and conventional fertilizer were evenly mixed for furrow application. The results showed that B3 treatment significantly improved the activities of urease，catalase and acid phosphatase in soybean rhizosphere soil. The soil β-glucosidase activity was the highest in B1 treatment during soybean vegetative growth and the highest in B4 treatment during reproductive growth. Biochar had no significant effect on soil sucrase activity. B3 treatment significantly increased the plant height，pod number per plant，effective pod number，grain weight per plant，100 grain weight and yield of soybean，and each factor increased by 13.13%，32.11%，45.73%，17.41%，7.80% and 7.35%，respectively，compared with the control. Biochar can improve soil enzyme activity and soil microenvironment. Combined with chemical fertilizer，biochar can significantly increase soybean plant height，effective pod number and 100 grain weight，so as to promote crop yield and income.