Abstract: A pot experiment was carried out to investigate the effects of nitrogen fertilization rates on the inter-competitiveness of a barley-pea intercropping system, and to quantify the relationship between the relative competitiveness and the production of crops for optimizing management of pastoral legume intercropping techniques in terms of nitrogen fertilization. Our results showed that the land equivalent ratio(LER) of barley was greater than one during crop tillering and grain-filling stages, indicating the intercropping advantage; whereas it was less than one during crop jointing and heading stages, indicating the inferior performance. With high levels of nitrogen(N2), the LER of barley during the tillering, jointing and grain-filling stages were 1.17, 1.03 and 1.34, respectively and were significantly higher than those with low levels of nitrogen(N1), indicating that a high nitrogen level may result in the certain intercropping advantage of barley. During the symbiotic period, the relative competitiveness(Abp) of barley under no nitrogen(N0), N1 and N2 were -0.1066, -0.2133, and - 0.1407 during the tillering stage, 0.0664, -0.0144 and 0.0276 at harvest, and 0.1328, 0.0425 and 0.0187 during the whole growing period, respectively, suggesting that nitrogen fertilization may adjust the Abp in the barley-pea intercropping system. Production of intercropping system was positively correlated with the Abp during the grain-filling stage, and correlated with the mean relative competitiveness in a form of quadratic curve. The average relative competitiveness of barley was 7.6% higher in N0 than that in N2, while it was less than zero in the N1 treatment. These results might suggest that an appropriate increase of the competitiveness advantage of barley during the grain-filling stage is helpful to improve the total production of a intercropping system. Therefore, nitrogen fertilization played an important role in impacting the relative competitiveness and the production of the barley-pea intercropping system.