Crop response to nitrogen (N) fertilization and N use efficiency (NUE) depend not only on N management, but also on water resource management and local climate. To the increasing environmental pollution induced by over-use of N in the irrigated areas, regulation of water-N management for achieving a win-win situation that will improve water use efficiency (WUE) and NUE has been still very concerned. Through literature reviews concerning water-N relations and their synergic management, as well as statistic data analysis with emphasis on an intensive wheat-maize cropping system in the North China Plain, the relationships between grain yields, water and N, as well as their use efficiencies under the regional climate conditions have been discussed. In the last 20 years, the research on water-N management in China has been involved in rainfed farming areas, and further in water-saving irrigated farming areas. The recent research focused mainly and continuously on the improvement of crop yields and WUE in dryland farming, and also on N-related environmental problems associated with N over-use in the irrigated areas. Currently, in the intensive double-crop (wheat and maize) rotation systems in the North China Plain, a large amount of N surplus in soils and low response of crop yields to N fertilization in the most crop fields have been continuously exposed with annually over-N fertilizer inputs (as reported above 500-600 kg?hm-2?a-1). The low response of crop yields to irrigation water in some crop fields has been also observed due to over-irrigation. This implies that there is still a big scope for improvement of WUE and NUE by using water-saving and N-reducing practices in the irrigated areas. For instance, with recommended fertilization practices the NUE by wheat and maize could be up to 50% and 34%, respectively, as compared those with conventional practices (14% and 20%, respectively). According to China statistics (1988-2007) in the regions of North China Plain, the changes in grain yields per ha showed significantly positive correlations with the mean air temperature annually, but little with the variations in rainfall. With the trend of declining annual rainfall and increasing annual air temperature, the Precipitation use efficiency (PUE) increased but NUE decreased significantly. Based on many previous studies on water-N relation, the synergic relations between water, nitrogen, and crop yields were found in a given range. The WUE generally increased with decreasing irrigation water or increasing N fertilizer amount, while NUE declined with increasing the amount of N fertilizer. The WUE and NUE can be improved by using water-saving and N-reducing practices, respectively. Limited irrigation combined with the proper amount of N fertilizer will be a viable alternative to the condition of climate warming, and drying. As reviewed on water-N research progress abroad, some disparities between China and advanced counties exist, thus, further researches especially in the aspects of field or regional simulations, predictions, real-time monitoring and plant diagnosis related to crop water-N synergic management are still needed.