Abstract: It is of great significance to investigate the competition relationships and complementarity effects among crops in intercropping systems under different nitrate/ammonium nitrogen ratios, which is important for elucidating the mechanisms driving system stability and guiding rational fertilization practices. Taking wheat (Triticum aestivum)-faba bean (Vicia faba) intercropping systems as subjects, this study designed different nitrate/ammonium nitrogen ratios: 4∶0 (N1), 3∶1 (N2), 2∶2 (N3), 1∶3 (N4), and 0∶4 (N5). The crop yields and biomass under monoculture and intercropping conditions were measured, and the land equivalent ratio, root/shoot ratio, aggressivity (A_WF), relative intensity of impact (RII), net effect (NE), compensatory effect (CE), and selection effect (SE) of intercropping were calculated to determine the effects of different nitrate/ammonium nitrogen ratios on interspecific competition and complementarity. The results showed that the land equivalent ratio of intercropping was greater than 1 under different treatment conditions. Among different treatments, N2 had the largest partial land equivalent ratio of faba bean. There were no significant difference in the aboveground or underground biomass of wheat in monoculture and intercropping under conditions N1 to N5. Among all the treatments, the A_WF of wheat was all greater than 1 and the greatest was under N2. Compared with other treatments, N2 increased the RII of wheat by 1.4–6.3 times (P<0.05). The CE of each intercropping system was greater than 0 and reached the maximum value under N2, and the SE of each intercropping system was less than 0. The A_WF and RII of wheat were obviously stronger than those of faba bean in wheat-faba bean intercropping systems. The RII of wheat and partial land equivalent ratio of faba bean had positive correlations with CE in the intercropping systems. In conclusion, different nitrate/ammonium nitrogen ratios affect the interspecific competition and complementarity in the wheat-faba bean intercropping systems, thus influencing the intercropping system yield. Treatment with a nitrate/ammonium nitrogen ratio of 3∶1 (N2) has the most significant interspecific competition and complementory effect.