Abstract: Nitrification driven by microorganisms is a key process in the nitrogen cycle. Soil ammonia oxidation is the first and rate-limiting step of nitrification, and nitrogen application can affect soil ammonia-oxidizing microorganisms. The effects of different nitrogen fertilizer types (urea, ammonium sulfate and potassium nitrate) on soil ammonia-oxidizing microbial community and nitrification potential are still in default of empirical evidence and should be identified to provide reference for alleviating farmland nitrogen loss and improving nitrogen cycle. In this study, calcareous purple soil was used as the research object, and four treatments of no fertilizer (CK), urea (UR), ammonium sulfate (AS) and potassium nitrate (PN) were set up by pot experiment. The effects of different types of nitrogen fertilizers on soil ammonia oxidation were clarified by measuring soil chemical factors, nitrification potential, community structure and diversity of soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). Our results indicated that, compared to CK treatment, AS and UR treatments significantly reduced soil pH by 2.52 and 0.32, and reduced C/N ratio by 40.0% and 20.0% (P<0.05), but significantly increased total nitrogen (TN) and ammonium nitrogen (NH₄⁺-N) content by 53.6%~83.0% and 1359.5%~1740.4% respectively (P<0.05); soil alkaline hydrolysis nitrogen (AN) and nitrate nitrogen (NO₃^--N) content were significantly increased by 164.9%~233.1% and 434.6~1485.3% among three N fertilization treatments (P<0.05); soil available phosphorus (AP) content was significantly reduced by 33.7% merely in AS treatment compared to the other three treatment groups (P<0.05); there was no obvious differs in soil organic carbon (SOC) content among different treatments (P>0.05); the lowest nitrification potential was found in AS treatment than those in the other three treatment groups, reduced by 42% relative to CK treatment, while nitrification potential was significantly increased by 292.0% and 62.6% respectively in UR and PN treatments (P<0.05). Moreover, AS and UR treatments significantly increased the amoA gene abundance of AOA by 84.1% and 44.4%, AS treatment significantly reduced the amoA gene abundance of AOB by 44.0%, and UR treatment significantly increased the amoA gene abundance of AOB by 1821.3% (P<0.05) compared to CK treatment, respectively. Redundancy analysis showed that pH and NH₄⁺-N were the main influencing factors of AOA community structure, while C/N, SOC and AN were the main influencing factors of AOB community structure (P<0.05). Stepwise regression analysis showed that were NH₄⁺-N and AN were the main influencing factors of the amoA gene abundance of AOA, while AP and AN were the main influencing factors of the amoA gene abundance of AOB (P<0.001). Partial least squares analysis showed that the amoA gene abundance of AOB, SOC, AP, AN and pH had significant effects on soil nitrification potential (P<0.05). Our findings suggest that, the application of ammonium sulfate significantly reduces the nitrification potential by increasing AN content and reducing AP content and the amoA genes abundance of AOB, while urea application increases the nitrification potential by increasing AN content and the amoA genes abundance of AOB. AOB community is the main driver of soil ammonia oxidation in calcareous purple soil. In calcareous purple soil, the application of different nitrogen fertilizers had different effects on ammonia-oxidizing microbial community and nitrification potential. Among them, the application of ammonium sulfate mainly reduced nitrification potential by increasing AN content, reducing AP content and the amoA gene abundance of AOB, while the application of urea mainly increased AN content and the amoA gene abundance of AOB , and finally increased the nitrification potential.