Early studies demonstrated that the land equivalent ratio (LER) of maize-soybean relay intercropping is greater than 1 , namely, maize-soybean relay intercropping can increase land productivity. However, previous studies focused on resource utilization in maize-soybean relay intercropping, and the distribution of roots belowground remains unclear [12, 19, 20]. Little information is available on the effect of reduced N on the yield advantage and increase in NUE in relay intercropping systems. Additionally, no evidence is available on the effect of reduced N inputs on facilitation in maize-soybean relay strip intercropping. Therefore, the aims of this study were (i) to evaluate the effect of reduced N input on crop grain yield and NUE in the maize-soybean relay strip intercropping system, and (ii) to assess the effect of reduced N input on crop roots distribution in the maize-soybean relay strip intercropping system, and (iii) to analyze the effects of crop roots distribution on crop growth in the maize-soybean relay strip intercropping system.