【Objective】Amendment of biochar has a significant impact on methane (CH₄) emission in paddy field, but it is still unclear about its mechanism, so further study should be done to clarify the issue and to provide a scientific basis for the use of biochar in the rice-wheat rotation system.【Method】Soil samples were collected from a paddy field of a field experiment on amendment of biochar and nitrogen (N) fertilizer after the crop of wheat was harvested in 2015 for analysis to assess effects of biochar and N fertilizer amendment on soil physiochemical properties, methane oxidation potential and methane production potential as well as gene abundances of methanotrophs and methanogens with the real-time PCR technology. Biochar was added once to the paddy field before rice transplanting on June 10, 2012. The field experiment was designed to have five treatments in triplicate, that is, Treatment N0B0 (no nitrogen (N) and biochar (B) amended) as control, Treatment N0B1 (only biochar amended, 20 t hm^-2), Treatment N1B0 (only N fertilizer amended, 250 kg hm^-2 urea), Treatment N1B1 (250 kg hm^-2 urea and 20 t hm^-2 biochar amended, and Treatment N1B2 (250 kg hm^-2 urea and 40 t hm^-2 biochar). 【Result】Results show that Treatments N1B1 and N1B2 significantly increased soil organic carbon and microbial biomass carbon (p < 0.05), and soil pH, too, as compared with Treatment N1B0 treatment. Moreover, the abundance of methanotrophs and methanogens were found significantly related to some soil physiochemical properties. Statistical analysis shows that the copy number of pmoA gene was significantly and positively correlated with soil microbial biomass carbon (r = 0.563, p < 0.05), but negatively with soil NH₄ -N content (r = -0.573, p < 0.05). In addition, the copy number of mcrA gene was positively related to soil total N (r = 0.675, p < 0.01), microbial biomass carbon (r = 0.713, p < 0.01) and soil organic carbon (r = 0.696, p < 0.01). Besides, methane oxidation potential was positively related to biochar application rate in the presence of N fertilizer (p < 0.05), and In Treatment N1B2, methane production potential increased from 0.001 mg kg^-1 h^-1 in Treatment N1B1 to 0.002 mg kg^-1h^-1. Methane oxidation potential was 44.4% higher in Treatment N1B1 than in Treatment N1B0, while being 31.6% lower than in Treatment N0B1. Relative to Treatment N1B1, Treatment N1B2 increased methane oxidation potential from 0.26 to 0.40 CH₄ mg kg^-1 h^-1. Treatment N0B1 significantly increased the log copy number of pmoA gene, from 6.56 g-1d.w.s in Treatment N0B0 up to 6.94 g-1d.w.s (p < 0.05). Compared with the control or Treatment N0B0, Treatment N1B0 inhibited increase in copy number of pmoA gene a certain extent, while increasing the copy number of mcrA gene by 3.0%, which indicates that nitrogen fertilizer can significantly stimulate growth of methanogens. Compared with Treatment N1B0, Treatment N1B2 was higher in copy number of both pmoA gene and mcrA gene, but Treatment N1B1 remained almost unchanged, which suggestes that biochar amendment at 40 t hm^-2 can significantly raise the abundance of methanotrophs and methanogens. Compared with Treatment N0B1, Treatment N1B1 greatly decreased pmoA/mcrA ratio from 1.01 to 0.94, and methane oxidation potential by 31.6%. However, biochar amendment increased pmoA/mcrA ratio in the treatments the same in nitrogen fertilizer level (p < 0.05).【Conclusion】All the findings in this experiment demonstrate that biochar amendment promotes methanotrophs and methanogens in abundane, but the effect is much higher on the former than on the latter, and consequently on methane oxidation capacity than on methane production potential. Therefore, it can be concluded that the practice of biochar amendment helps mitigate methane emissions in the paddy field during the wheat growing season.