To get insights into the effects of some common fertilization treatments on acidification of an alkaline soil in greenhouse system, long-term fixed-plot experiments were conducted. The pHw (determining in suspension of soil in water without CO₂) and pHCa (determing in 0.01 mol/l CaCl₂) of all the treatments decreased significantly after three consecutive crops, indicating that fertilizations caused soil acidification. There were no differences in the amounts of nitrogen and excess cations absorbed by crops between the U (urea, single superphosphate and potassium sulfate were used as base fertilizer, and urea was also used as topdressing) and CF (nitro-compound fertilizer, urea and potassium sulfate were used as base fertilizer, and urea was also used as topdressing) treatments. The same amount of nitrogen was applied for the two treatments. Therefore, there are no differences in soil pH values between U and CF treatments. Application of organic fertilizer increased the total amounts of nitrogen and excess cations absorbed by crops, leading to the significant decrease in soil pH of 10-20 cm layer. Hence, the organic fertilizer promoted the acidification of the alkaline soil. However，the acidification of alkaline soils is beneficial to crop growth and its negative effects can be ignored.