In order to explore the applicability of critical nitrogen dilution curve and the feasibility of nitrogen surplus evaluation for summer maize in Guanzhong Region, Shaanxi Province, two nitrogen fertilizers: urea (N 0, 80, 160 and 240 kg/hm2, 40% of N fertilizer applied as basic and 60% top dressed at bell stage) and controlled-release fertilizer (N 0, 60, 120, 180 and 240 kg/hm2, all applied as basic fertilization) were chosen to determine critical nitrogen concentration dilution curve based on field experiments in 2013 and 2014. Models of nitrogen uptake, nitrogen nutrition index and accumulative nitrogen deficit were established to diagnose nitrogen nutrition status of maize plant according to the critical nitrogen concentration. In addition, nitrogen use efficiency was compared among different nitrogen application rates treatments. The results showed that a negative power function correlation between maximum aboveground dry matter and critical nitrogen concentration was existed. Calibrations (using the data series of 2014) indicated that these models had high reliability with relative error of 0.46%~4.08%. The nitrogen nutrition index model and the accumulative nitrogen deficit model could be used to diagnose plant nitrogen status effectively and regulate nitrogen fertilizer management quantitatively. The appropriate nitrogen application rate of urea and controlled-release fertilizer for maize growth was 160~174 kg/hm2 and 120~150 kg/hm2, respectively. Compared with urea, controlled-release fertilizer could significantly increase the nitrogen use efficiency and save nitrogen amount approximately by 14% for maximum yield (urea: 10.73 t/hm2; controlled-release fertilizer: 11.01 t/hm2).The investigation is beneficial to the dynamic and precise fertilization, nitrogen management optimization and effective utilization of resources both on theoretical and technical sides.