Abstract: An Ultisol from cropland in Anhui Province in subtropical China was used to study the effects of urea, ammonium sulfate (NH4)2SO4 and ammonium bicarbonate NH4HCO3 on nitrification and acidification of the soil with incubation experiments. Nitrification increased significantly with nitrogen fertilizers added. The net nitrification rate of the control soil was (NO2-+NO3-)-N 25.7mol /(kg?d), the corresponding figures were (NO2-+NO3-)-N 51.3189.6, 50.7149.9 and 60.5107.9 mol /(kg?d) for the treatments with urea, NH4HCO3 and (NH4)2SO4 added, respectively. Greater addition of urea and NH4HCO3 led to a more increase in net nitrification rate, however, the highest net nitrification rate occurred when N 150 mg /kg soil was added for (NH4)2SO4 treatment. Meanwhile, soil pH decreased by 0.110.43, 0.020.36 and 0.080.26 pH units for the treatments of urea, NH4HCO3 and (NH4)2SO4 compared with the control, respectively. There was a significant negative correlation between the soil pH and the content of (NO2-+NO3-)-N. Soil acidification rate was also linearly correlated with nitrification rate, confirming that nitrification in soil was the main cause for accelerating acidification of the Ultisol.