Crop row spacing in intercropping systems affects interactions of crop species and subsequent crop yields. In a field experiment, the response of crop yield to different maize row spacing (0-80 cm) in pea/maize intercropping system was investigated. The results showed that land equivalent ratio (LER) of each treatment exceeded 1, indicating a significant yield advantage. When maize row spacing changed from 0 cm to 80 cm, the system yield first increased to a threshold and then declined. Positive quadratic relations between maize row spacing and yields of intercropping system or intercropped maize were observed in the field experiment. The highest yield occurred when maize row spacing was 40 cm and intercropped maize yield reached 10,118 kg ha². Since intercropped pea yield never changed significantly, yield of the intercropped pea/maize system was dependent on maize yield. The change in maize row spacing significantly influenced maize yield components and especially grain number per spike. Grain number per spike (549 grains per spike) was highest when maize row spacing was 60 cm. Maize aggressive dominance over pea in terms of yield gradually strengthened with increasing maize row spacing. When maize row spacing was within 60 cm, its aggressive dominance over pea was below zero. This indicated that maize had a stronger competitiveness than peas. However, when maize row spacing was 80 cm, its relative aggressive dominance was 0.14 — which suggested that pea was more competitive than maize. Hence adjustment of maize row spacing effectively enhanced maize yield in pea/maize intercropping system. This increased production output of pea/maize intercropping system.