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A field experiment under film mulched drip irrigation was conducted for two consecutive years (2014.5-2015.10) in the Northeast Plain of China (NEC), in order to quantify the maize yield-increasing potential and optimum nitrogen (N) level. The results showed that mulched drip irrigation significantly promoted the environmental factors, maize growth and production in the NEC (p <= 0.05). Compared with the traditional rain-fed management, the total soil water storage (SWS) at ridge significantly increased by 80 mm and the topsoil accumulative temperature (TC) increased by 353 degrees C under mulched drip irrigation. Compared with non mulched surface drip irrigation, the total SWS and TC also increased by 9 mm and 245-314 degrees C under mulched drip irrigation. The increased TC was the main reason for the promotion of crop development in the early stage, and it prolonged the duration from tasseling stage (VT) to physiological maturity (R6) and increased the yield. Furthermore, the soil total N at the root zone and N uptake also increased under mulched drip irrigation, about 0.28 g/kg and 28.41 kg/hm(2) higher than local management, respectively, which could be regarded as the second reason for the yield-increase. The third main reason for the increase in yield was that more net radiation was intercepted by maize under mulched drip irrigation. Compared with local maize cultivation, the maize yield increased by 10%-29%, and water use efficiency (WUE) increased by 10%-31% and nitrogen use efficiency (NUE) increased by 57%-84% at 230 kg/hm(2) N under mulched drip irrigation. There was no significant yield increasing (p > 0.05) with N changed from 230 kg/hm(2) to 330 kg/hm(2). Therefore, N of 230 kg/hm(2) was recommended for mulched drip-irrigated maize and an increase of more than 10% of yield and WUE was validated by mulched drip irrigation experiments in the NEC.