The long-time excessive application of N fertilizer caused detrimental effects on soil and groundwater environment in North China Plain (NCP). Therefore, the reasonable water and N managements are essential for the sustainable agricultural production in this region. A two-year field experiment (2010—2011) was carried out in the wheat—maize rotation cropping field at Tongzhou Experimental Base for Water-saving Irrigation Research (TEB), Chinese Academy of Sciences, Tongzhou District, Beijing, China. The collected data in the experiment was used to calibrate and validate the hydrologic, nitrogen and crop growth components of the root zone water quality model (RZWQM). And the validated RZWQM was used to evaluate N fertilizer and water management practices in wheat—maize rotation cropping system under sprinkler irrigation system in NCP. The validation results showed that the RMSE (root mean square errors) and MRE(mean relative error) for soil water content ranged from 0.015cm3/cm3 to 0.026cm3/cm3 and from -6.66% to 5.83%, respectively. The simulated soil water storage was close to the measured ones. The relative errors (RE) of measured and predicted crops yields and N uptakes of winter wheat and maize were generally less than 25%. The RZWQM was used to simulate the dynamics of soil water and nitrogen in the wheat—maize rotation cropping system under different irrigation interval when N application was the same to local N management (330kg/hm2). Results showed that the crop yields were higher, however, NO3-N leaching and mean N losses were less at irrigation interval with accumulated pan evaporation of 30~70mm than those at irrigation interval with pan evaporation of 90~110mm. Therefore, sprinkler irrigation interval with pan evaporation of 30~70mm was recommended in wheat—maize rotation system in NCP.