In the present study, a 9-year field experiment was conducted to investigate the effects of straw returning on the rhizosphere ammonia-oxidizers and nitrification in a red soil. The field experiment included five treatments:no fertilizer, CK; chemical nitrogen, phosphorous and potassium fertilizer, NPK; NPK fertilizer and straw, NPKS; NPK fertilizer and straw combined with pig manure, NPKSM; NPK fertilizer and straw biochar, NPKB, which was located at the National Agro-Ecosystem Observation and Research Station in Yingtan. Here, the abundance and composition of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in the rhizosphere of maize under different types of straw returning were examined by quantitative PCR and Illumina sequencing. The results found that the straw returning treatments significantly increased soil nutrient contents and potential nitrification activity (PNA) compared with the CK and NPK treatments, with the highest soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), available phosphorus (AP), available potassium (AK), nitrate nitrogen (NO₃^--N), ammonium nitrogen (NH₄⁺-N) and PNA under the NPKSM treatments. AOA-specific PNA (PNA_AOA) was significantly higher than AOB-specific PNA (PNA_AOB), which indicated that AOA dominated the nitrification in a red soil. The straw returning treatments presented significantly higher abundance and diversity (Shannon and Chao1 indices) of AOA and AOB community than the treatments without straw returning. Furthermore, the straw returning treatments significantly shaped the composition of AOA and AOB community. SOC, TN, NH₄⁺-N, as well as AOA and AOB diversity were significantly correlated with PNA_AOA and PNA_AOB, respectively. Structural equation modelling showed that NH₄⁺-N and TN indirectly affected PNA_total through the AOA abundance and AOB diversity. The results indicated that straw returning treatments could improve the abundance and activities of AOA and AOB community, and consequently promoted the process of nitrogen transformation, with the best improvement achieved by straw and pig manure application.