Effect of application of ammonium-based N (NH ₄ ⁺) on N₂O emission was investigated in typical subtropical soils in China. Soil samples, collected from upland crop field (SU), brush-land (GB) and forestland (QF), were incubated with temperature kept at 30℃ and soil moisture at 60% of the water hold capacity (WHC) for 35 days after addition of ammonium sulphate, urea, and ammonium bicarbonate, separately. Each type of N fertilizer had three different application N rates 0, 100, and 250 mg kg^-1. Results indicate that in SU soil (pH=6.27), both nitrification and N₂O emission were stimulated by addition of ammonium sulphate, urea and ammonium bicarbonate. Net nitrification and N₂O emission increased with the fertilizer application rate. In acid GB (pH=4.82) and QF soils (pH=4.46), addition of ammonium sulphate inhibited nitrification, but dramatically stimulated N₂O emission; addition of urea and ammonium bicarbonate slightly stimulated nitrification, but slightly inhibited N₂O emission or showed no effect on both. Significant negative correlation was observed between the ratio of N₂O emission to net nitrification in acid soils treated with different forms of N fertilizers and the soil pH measured immediately after addition of N fertilizer. Mechanisms of the effects of different forms of N fertilizers on ratio of N₂O emission to net nitrification need to be further investigated.