Nitrogen fertilizer reduction and efficiency enhancement is one of the important measures to achieve zero growth of chemical fertilizers in China，the biological effects and nitrogen fertilizer utilization ratios of different biochar and nitrogen fertilizer ratios were explored to provide a basis for the efficient use of straw biochar in yellow soil paddy field.Field experiment was carried out to study how partial substitution of mineral N with biochar affected rice yield，rice quality，nitrogen uptake，and nitrogen use efficiency of rice in yellow soil of Guizhou.There were 6 treatments:control CK (no nitrogen fertilizer)，conventional fertilization T0 (100% mineral nitrogen)，T1 (10% biochar nitrogen + 90% mineral nitrogen)，T2 (20% biochar nitrogen + 80% mineral nitrogen)，T3 (30% biochar nitrogen + 70% mineral nitrogen)，T4 (40% biochar nitrogen+60% mineral nitrogen).The results showed that rice yield increased firstly and then decreased with the increase in the ratio of biochar nitrogen and fertilizer nitrogen，and got the maximum under T2，which was significantly increased by 13.4% comparing to T0 (P<0.05).Compared with T0 treatment，the combined application of biochar and nitrogen fertilizer reduction can significantly affect milled rice rate，gum consistency and amylose content，and T2 treatment is better.Compared with T0，nitrogen accumulation in straw under T1，T2 and T4 increased by 4.5%～17.3%，and T2 treatment was significant (P <0.05)；nitrogen accumulation in grain under T1，T2 and T3 increased by 31.1%，27.3% and 21.8%，respectively；Partial nitrogen productivity，agronomic efficiency，and apparent nitrogen use efficiency under T1，T2 and T3 increased by 2.4%～13.3%，8.2%～46.3% and 8.87～22.41 percentage point，in which T2 was significant；The nitrogen harvest index increased under T1，T2，T3 and T4，but none was significant.The above results indicate that partial substitution of mineral N with biochar can increase rice yield and nitrogen fertilizer use efficiency in yellow paddy soil paddy，and improve rice quality.Under short-term condition，substitution of 20% mineral N with biochar N is recommended as the optimum ratio for medium-fertility yellow paddy soil.