Abstract: Intercropping systems have competitive and synergistic effects on nutrient uptake and utilization due to differences in crop combinations and belt configurations and the differences in nutrient uptake and utilization between different intercropping systems are also large. Reasonable intercropping patterns can improve the microenvironment of the crops by adjusting the field configurations of crop side-row ratios, widths, and spacings to improve the utilization of resources and the yields of the crop groups. To clarify the differences in the contribution of crop nutrient uptake and utilization to yield in oilseed flax||maize, and oilseed flax||soybean systems, we used a two-factor randomized block trial design in the field. Two types of intercropping were set up: oilseed flax||maize intercropping (F||M), oilseed flax||soybean intercropping (F||S), with three belt configurations 4∶2 (S1), 6∶3 (S2), and 8∶4 (S3), for a total of nine treatments, with monocropping as the control, to comparatively analyze the intercropping advantages of different belt configurations and the contribution of nutrient uptake and utilization efficiency to intercropping advantages at maturity in oilseed flax||maize, and oilseed flax||soybean intercropping systems. The results showed that intercropping increased crop biomass yield and seed yield compared with monocropping. The oilseed flax||maize was significantly higher than oilseed flax||soybean intercropping systems, reaching a maximum in the 8∶4 row ratio configuration. Both intercropping systems had a land equivalent ratio (LER) greater than 1, indicating a yield advantage. In oilseed flax||maize system, it showed increase in the total plant uptake of nitrogen, phosphorus, and potassium, ranging from 12.15% to 50.38%, 44.79% to 67.29%, and 3.90% to 25.75%, respectively, when compared to monocropping; nitrogen utilization efficiency was observed to be 73.20%–78.36% higher in the intercropping system than that in the monocropping system; the efficiency of nitrogen, phosphorus, and potassium uptake contributed to the land equivalent ratio (LER) with values ranging from 1.33 to 2.10, 1.76 to 2.08, and 1.11 to 1.53, respectively; the utilization efficiency showed negative contributions ranging from −0.30 to −0.12, −0.42 to −0.25, and −0.10 to 0.07 for nitrogen, phosphorus, and potassium, respectively. In the oilseed flax||soybean system, total nutrient uptake of nitrogen, phosphorus, and potassium were 6.86%–60.06%, 11.97%–59.21%, and 7.34%–65.30% higher than that in the monocropping system; Nitrogen utilization efficiency was 48.77% to 71.74% higher than that of monocrops; contributions of nitrogen, phosphorus, and potassium uptake efficiencies to LER were 1.17 to 2.13, 1.20 to 2.10, and 1.15 to 2.15, respectively, and the contributions of utilization efficiencies were −0.53 to −0.30, −0.46 to −0.15, and −0.52 to −0.03, respectively. Based on the above, the intercropping system with 8-row oilseed flax and 4-row maize belts enhances crop nutrient uptake and utilization capacity. The increase in crop yield in the intercropping system was primarily due to nutrient uptake increased rather than changes in utilization efficiency.