Though the reclaimed land is an important reserve land resource,it usually is poor in soil structure and low in organic matter and nutrient content.Organic fertilizer can quickly improve soil productivity,yet it will cause large emissions of greenhouse gases such as Nitrous Oxide (N₂O).It has been proved that the inoculation of Plant Growth-Promoting Rhizobacteria (PGPR) with N₂O reduction function not only reduces greenhouse gas emissions but also promotes crop growth.In this study,a PGPR denitrificans YSQ030 with N₂O reduction function was used as the test strain to clarify the effect of YSQ030 on N₂O emission and nitrogen cycling key functional genes in reclaimed soil with organic fertilizer application.Soil microcosmic experiments were set up for application of organic-inorganic compound fertilizer and sheep manure,then the soil N₂O emission fluxes after inoculation of YSQ030 were analyzed by gas chromatography.Meanwhile,soil chemical properties were analyzed at the end of the experiment,and the abundance of soil nitrification and denitrification functional genes (AOA amoA and AOB amoA;nirS,nirK,nosZ Ⅰ and nosZ Ⅱ ) were analyzed by real-time quantitative PRC.The results showed that YSQ030 significantly reduced the N₂O emission of reclaimed soil with organic-inorganic compound fertilizer or sheep manure,with the maximum reduction of N₂O emission reaching 91.5％ and 30.9％,respectively.The N₂O emissions of organic-inorganic compound fertilizer treatment were much higher than those of sheep manure treatment,which may be due to the low abundance of N₂O reductase genes of nosZ Ⅰ and nosZ Ⅱ in the former treatment.Furthermore,significant reduction of the abundance of nitrification and denitrification functional genes were observed only in organic-inorganic compound fertilizer treatments.This study shows that YSQ030 can reduce the N₂O emission in soil applied with organic fertilizer,which can provide a scientific basis for both soil fertility improvement and N₂O emission reduction,and also provide core strain resources for the research and development of new microbial fertilizers or bio-organic fertilizers.