A pot experiment was carried out in apple-Trifolium repens Linn. (M1) and apple-Lolium perenne L. (M2) intercropping system to investigate the effects of root interaction on the growth and ¹⁵N-urea absorption, utilization, loss and residue of apple trees under different root barrier method (N1, N2 and N3 were equivalent to solid barrier, mesh barrier and no barrier, respectively), using the ¹⁵N-labeled tracer technique. Results showed that, at new shoot growing stage, the growth index of apple trees displayed an order of N3 > N2 > N1 in M1 intercropping system, while the opposite tendency was observed in M2 intercropping system. Compared with N1 treatment, the ¹⁵N utilization rate of apple trees increased by 11.91% and 18.96% in M1 intercropping system under N2 and N3 treatment, but decreased by 5.76% and 8.99% in M2 intercropping system. The plant total N content and ¹⁵N absorption amount showed the same tendency. The effect on ¹⁵N abundance and total N content in the soil of apple trees were the most significant in N1 treatment, and the least in N3 treatment. At leaf fall period, the growth index of apple trees was obviously the highest in N3 treatment, and the lowest was found in N1 treatment. In comparison with N1 treatment, the soil ¹⁵N abundance of apple trees under N2 and N3 treatment increased by 22.33% and 34.15% in M1 intercropping system, and the rate of increase in M2 intercropping system were 13.73% and 21.44%, the total N content in the soil of apple trees showed the same tendency. There were significant differences in plant total N content,¹⁵N absorption amount and Ndff value among the treatments, which was in a trend of N3 > N2 > N1 in M1 and M2 intercropping system. The ¹⁵N utilization rate of apple trees under N2 and N3 treatment were 19.11% and 42.66% higher than that of N1 treatment, with the ¹⁵N loss rate were 13.55% and 27.12% lower than that of N1 treatment in M1 intercropping system, the same trend was showed in M2 intercropping system. Overall findings showed that it mainly showed a competitive effect in apple-Lolium perenne L. intercropping system and a relatively minor positive effect in apple-Trifolium repens Linn. intercropping system during early stages of apple growth. While in the later period of apple growth, the root interaction in forage grasses and apple trees reduced nitrogen loss and consequently improved the absorption, utilization of nitrogen nutrition and the growth of apple trees by a certain degree, and Trifolium repens Linn. played a better effect than Lolium perenne L.