Wetland, one of the most important ecosystems in the world, plays a significant role in global C and N cycles. Although the majority of studies to date have been centered on wetlands as CH₄ sources, wetland soils can however also act as CH₄ sinks. It has been recognized that Sanjiang Plain palustrine wetland (45°01'-48°28'N, 130°13'-135°05'E), one of the largest palustrine wetland areas in China, play a significant role in the estimation of CH₄ budgets. To find the influence of nitrogen fertilizer on CH₄ oxidation in mire soils, the fresh mire soil from Sanjiang Plain was amended with 0, 25 or 50 mg(N)/l NH₄HCO₃ and incubated at 25℃ over six consecutive periods: first at atmospheric CH₄ concentration (about 1.8 μL/L), then at elevated CH₄ concentration (about 8000 μL/L) for four times, and finally at concentration of about 1.8μL/L. The addition of NH₄HCO₃ resulted in reduction in the rate of CH₄ oxidation approximately in inverse proportion to the amount of NH₄HCO₃ added. At ~8000 μL/L, the initial inhibitory effect was gradually released and disappeared during subsequent incubations. Finally, NH₄HCO₃ addition stimulated the CH₄ oxidation. NH₄HCO₃ addition stimulated the rates of CH₄ oxidation by the mire soil at atmospheric CH₄ concentration during the final incubation. The initial inhibitory effect of NH₄HCO₃ addition on CH₄ oxidation at both atmospheric CH₄ concentration and high CH₄ concentration in mire soil is temporary, and the long-term effect of NH₄HCO₃ addition may be stimulating.