Abstract: Acidic forest peat soil in Xiaoxing’an Mountain was used to investigate the type and key drivers of nitrification by carrying out nitrification incubation after adding 10 mL·L^-1 C₂H₂ and different amounts of (NH₄)₂SO₄(0, 1.2, 6.0 mmol N·kg^-1). Results showed that strong mineralization (0.9-1.4 mg N·kg^-1·d^-1) and nitrification (0.4-0.6 mg N·kg^-1·d^-1) after 2 weeks of incubation were observed for both nitrogen and no nitrogen treatments, and no significant difference was observed for different (NH₄)₂SO₄ application treatments. For C₂H₂ treatment, there was relatively stronger mineralization (0.8 mg N·kg^-1·d^-1), but no obvious nitrification (0 mg N·kg^-1·d^-1). These results indicated that the nitrification in acidic peat soil was mainly autotrophic, and inorganic nitrogen application did not affect nitrification rate significantly. Results also implied that the substrate (NH₃) for nitrification was from the organic N mineralization, rather than the (NH₄)₂SO₄ application. Both ammonia-oxidizing bacteria (AOB) and archaea (AOA) abundances increased significantly during 0-14 d regardless of nitrogen application. However, no significant difference in AOB and AOA abundances for different (NH₄)₂SO₄ application treatments was observed, indicating that ammonia oxidizers did not respond positively to (NH₄)₂SO₄ application. Compared with the treatments without C₂H₂, AOB and AOA abundances did not change significantly during the incubation in C₂H₂ treatment, suggesting that both AOA and AOB were likely the key players in nitrification in the acidic peat soil.