Excessive application of nitrogen fertilizers in facilitated vegetable fields may easily lead to soil degradation (such as soil salinization, acidification, hardening, etc.),and even further to some serious environmental consequences like pollution of groundwater and emission of large volumes of N_2O, thus seriously affecting sustainable development of the vegetable industry. Recently, a novel soil remediation technology, called RSD (reductive soil disinfestation) has been developed of adding organic substances(e.g., crop straw, molasses, manure, etc.) in flooding water. The RSD method can effectively alleviate the risk of soil degradation, such as removing the nitrate accumulated in the soil, increasing pH, lowering soil electrical conductivity and improving soil structure. However, in strong reducing environments the high amount of nitrate accumulated in the degraded facilitated vegetable fields was rapidly reduced by denitrification, and high nitrous oxide (N_2O) emission was observed in RSD process. N_2O is the third major greenhouse gas, and is 296 ~310 times as high as CO_2 in global warming potential. It is estimated that N_2O emitted from agricultural soil accounts for 60% of the annual anthropogenic emission into the atmosphere, and the facilitated vegetable soil with high N input is one of the most important agricultural N_2O sources, contributing about 20% to the emission from agricultural soil. Therefore, it is essential to investigate how to mitigate N_2O emission from degraded facilitated vegetable soil, especially in its strong reductive remediation process. In this study, Biochar was selected as soil regulator in evaluating effects of the use of biochar on N_2O emission in degraded vegetable soil and its RSD process relative to rate of its use. Six treatments were designed and conducted, Treatment CK (16% in soil moisture content and no biochar used),Treatment 1% BC (16% in soil moisture content and 1% biochar applied, w/w),Treatment 5% BC (16% in soil moisture content and 5% biochar applied), Treatment RSD (flooded, rice straw incorporated and no biochar used), Treatment RSD + 1% BC (RSD and 1% biochar applied) and Treatment RSD + 5% BC (RSD and 5% biochar applied). By determining the abundance of nitrifying functional genes (norB gene and nosZ gene encoding nitric oxide reductase and nitrous oxide reductase, respectively),activities of denitrifying microorganisms were characterized. Soil samples were collected from the treatments and incubated at 30 Ti in dark for 14 days, and N_2O emission rate was measured during the incubation using the accumulative method. Besides, soil samples were also collected for analysis of inorganic nitrogen contents, soil pH and abundance of denitrifying functional genes. Each sampling had four replicates. Results show that RSD significantly lowered soil nitrate content, raising soil pH and retarded soil degradation, but the cumulative N_2O emission from the RSD-treated soils was over 950 times as high as that from their non-RSD treated counterparts. Application of 5% Biochar reduced the N_2O emission in degraded vegetable soil and its RSD process by 68.7% and 16.0%, respectively. Pearson correlation analysis reveals a negative relationship between N_2O emission rate and soil pH in both degraded vegetable soil and its RSD process, and a positive relationship between N_2O emission rate and soil ammonium content in RSD process.