Abstract: 【Objectives】To explore the effect of biochar made of maize straw on the soil fertility and nitrogen agronomic responses will provide theoretical and practical support for the straw resources utilization and soil fertility improvement in the maize belt in the Northeast China.【Methods】 Field experiment was conducted with maize straw and maize straw derived biochar (fast pyrolysis at 500℃ under low oxygen) in the black soil region in Northeast China. Three treatments were designed: 1) PK+maize straw; 2) NPK+4 t/hm2 maize straw; 3) NPK+2 t/hm2 maize straw+biochar from 2 t/hm2 maize straw. The plant and soil samples (0-20 cm) were collected at harvest, the relative items were analyzed with regular methods.【Results】 1) Compared with treatment 2 in 2013 and 2014, the soil available N in treatment 3 was significantly increased by 10.1% and 9.7% (P0.05), the soil available P by 13.7% and 27.3% with a significant improvement at 2014 (P0.05), the soil microbial biomass carbon (SMBC) by 13.5% and 26.9%, the soil urease activity by 22.3% and 31.8% respectively. The SMBC and the soil urease activity significantly improved in 2014 (P0.05). The soil organic matter, soil total N, available K, SMBN and soil sucrase activity were not improved significantly. 2) Analysis of nitrogen agronomic responses showed that the N partial factor productivity in treatment 3 was enhanced by 3.3% in 2013 and significantly by 9.6% in 2014 (P0.05); the benefit of economy of applied N (EBN) was increased by 12.9% in 2013 and significantly by 27.5% in 2014 (P0.05); while the yield, the N fertilizer use efficiency (UEN) and the agronomic efficiency didn't show significant increase.【Conclusions】 Biochar are more effective to improve the activities of soil microbe and the soil enzymes, and so to enhance the soil nutrient supply for maize. The nitrogen agronomy effect will be improved as a result. The application of maize straw as biochar is an effective way for straw efficient utilization in Northeast China.