Efficient nitrogen (N) management is critical for improving productivity and sustainability in intercropping systems, especially in semi-arid regions. Maize and peanut, the two dominant local crops, were selected to represent a typical cereal/legume intercropping system with contrasting nitrogen acquisition strategies. To investigate how spatial configuration regulates nitrogen uptake and nitrogen use efficiency in maize/peanut intercropping systems, a 3-year field (2022-2024) experiment was conducted on sandy soils in semi-arid northwest Liaoning, China. Six cropping systems were evaluated, including sole maize, sole peanut, and four intercropping configurations differing in strip width and crop proportion, including M2P2 (two rows of maize intercrop with two rows of peanut, M indicates maize and P indicates peanut), M2P4, M4P4, and M8P8. The total land equivalent ratio (LER) varied from 0.65 to 1.09, indicating that yield advantages were highly dependent on spatial configuration. Maize consistently exhibited stronger competitiveness than peanut, resulting in suppressed peanut growth in narrow-strip systems. Increasing strip width and peanut proportion alleviated interspecific competition and improved fertilizer nitrogen equivalent ratio (FNER) and nitrogen equivalent ratio (NER) in intercrops. Although intercropping did not consistently enhance total nitrogen uptake, nitrogen use efficiency was significantly improved. Narrow-strip systems (M2P2 and M2P4) increased nitrogen use efficiency, whereas wide-strip systems (M4P4 and M8P8) achieved yield benefits mainly through enhanced nitrogen uptake. Overall, the results highlight that spatial configuration plays a key role in regulating nitrogen uptake and interspecific competition in maize/peanut intercropping under semi-arid sandy conditions. Optimizing strip width and crop proportion is therefore critical for stabilizing yield and improving resource use efficiency in maize/peanut intercropping systems in dryland agriculture.