Plantations of saline-alkali tolerant rice in coastal areas are proposed as a strategy to improve rice yield and ensure global food security. The soil nitrification process driven by ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) is an integral part of the soil nitrogen cycle and correlates with the quality of coastal solonchak. However, little is known about the effects of saline-alkali tolerant rice cultivation on the soil nitrification process in coastal solonchaks. In this study, we investigated the community structures of AOA/AOB and the nitrification rate in the rice rhizosphere along salinity gradients. The abundance and nitrification rates of AOA and AOB declined with increasing salinity. Saline-alkali-tolerant rice cultivation significantly increased the abundance of AOA and AOB amoA genes from (3.09–11.5) × 106 and (7.76–52.0) × 105 copies g−1 in soils to (16.2–50.9) × 106 and (69.2–423) × 105 copies g−1 in the rhizosphere, respectively. Compared with bulk soils, the nitrification rate of AOA and AOB in the rhizosphere increased significantly with salinity. Saline-alkali-tolerant rice cultivation enhanced the nitrification process of saline-alkali tolerant soil by increasing the nitrification contribution of AOB. Our findings offer new clues on the accelerated nitrification process in the saline-alkali tolerant rice rhizosphere in coastal solonchaks and reveal its roles in shaping AOA/AOB communities, providing suggestions for saline-alkali tolerant rice plantations in coastal solonchaks.