【Objective】Nitrogen recycle is an important process in soil ecosystem, and soil microorganisms play a key role in the processes of nitrogen transformation. Nitrification is the process of soil microbe oxidizing ammonia into nitrate，involvingammonia-oxidizing bacteria (AOB)and nitrite-oxidizing bacteria (NOB), sequentially. But now,discovery of the microorganisms(Comammox)that can complete ammonia oxidization raised a number of fundamental questions. Purple soils is mainly distributed in the subtropical areas of China, particularlyin Sichuan Basin, playing a very important role in agricultural productionof the country. By pH and carbonate content,they can be divided into acidic, neutral and calcareous purple soils. Soil pH is an important factor not only affecting soil nitrification, but also influencing nitrification microorganisms in population and community structure. So what are the differences betweenpurple soils different in pH in nitrification and nitrifying microbial community? These scientific questions need to be answered.【Method】Samples of purple soils different in pH, i.e. acidic purple soil (pH=5.3) and neutral purple soil(pH=7.2) in Yongchuan of Chongqing and calcareous purple soil(pH=8.5) inYanting of Sichuan were collected for in-lab incubation to explore nitrification, soil microoganisms andcommunity structures of nitrifying microorganismsin the soils, using the stable isotope probing technique and Miseq sequencing.The incubation experiment was designed to have three treatmentsfor each soil sample, including ¹³CO₂ labeling, ¹²CO₂ control and ¹³CO₂+C₂H₂ control.Soil samples were cultured in aincubatorat 28℃ for 56 days, during which 100 mg kg^-1 urea-N and corresponding volume of gas was applied every week.Samples at D0 and D56 were analyzed with the Miseq sequencing technique. 【Result】Intense nitrification, dominantly autotrophic nitrification, was observed in both neutral purple soil (pH=7.2) and calcareous purple soil (pH=8.5),but not in acid purple soil (pH=5.3).In all the three types of purple soils, bacteria ofProteobacteria,Acidobacteria,Firmicutes,Chloroflexi,Actinobacteria,Bacteroidetes and Gemmatimonadetes were detected, but varied in proportion. Bacteria ofProteobacteria accounted for about 20% of the total in all thethree purple soils.In addition, Planctomycetes was detected in acidic purple soil. In the neutral purple soil and calcareous purple soil, Armatimonadetes and Verrucomicrobia were detected. NOB/AOB ratio reachedas high as 13 in all the three purple soils,which means that the Comammox may play an important role in the process of nitrification in purple soils. 【Conclusion】 In a word, the nitrification in the purple soils was mainly of the autotrophic type. Bacteria of Proteobacteria,Acidobacteria,Firmicutes,Chloroflexi,Actinobacteria,Bacteroidetesand Gemmatimonadeteswere detected in all the three types of purple soils.Distribution of the soil microbial community varied with the soil. Nitrosospira and Nitrospira was the numerically dominant genus of ammonia-oxidizing bacteria(AOB) and nitrite-oxidizing bacteria(NOB), respectively, in the three purple soils. NOB was higher than AOB in relative abundance.All these findings may serve as scientific basis for further study of nitrification in purple soils.