Abstract: A field experiment was conducted to investigate the effects of lower irrigation limits (W), pure nitrogen application rates (N) and planting densities (D) on seed maize yield and the three factors optimum combination under mulch drip irrigation in Shiyanghe Experiment Station of China Agricultural University in Gansu Province which was located in an arid region of Northwest China. The field orthogonal experiment had three factors, each factor included three levels. Results showed that: (1) the interaction effects of the three factors on grain yield, grain number and 1000-grain weight were not obvious; (2) when the planting density was within 85500-120000 plants/hm2, the effect sequence of different factors on the yield and grain number of seed maize was: W＞D＞N (primary→secondary), and that on 1000- grain weight was D＞N＞W (primary→ secondary). The best combination was W2N2D2 for seed maize planting under drip irrigation with mulch when the wide row spacing was 70 cm and the narrow row spacing was 40 cm.