[Objective] The aboveground biomass distribution variation and competition intensity of wolfberry (Lycium barbarum)-alfalfa (Medicago sativa) intercropping were studied in order to provide a scientific basis for interspecific allocation regulation and sustainable management of forest-grass intercropping. [Methods] Aboveground biomass samples of wolfberry and alfalfa were acquired by the spatial segmentation method. The distribution variation and spatial competition of the aboveground biomass of each component in the intercropping model were quantitatively analyzed. [Results] Under monoculture conditions, the aboveground biomass of wolfberry trees in the horizontal direction was distributed in the range of 0—90 cm from the wolfberry row, and decreased with increasing distance from the wolfberry row. The distribution of above-ground biomass of wolfberry in the horizontal direction at 40—60 cm above the soil surface moved to the direction of the row of wolfberry when intercropped with alfalfa, and the gravity center of the distribution of above-ground biomass of wolfberry moved upward in the vertical direction at 60—80 cm above the soil surface. The competitive ability of alfalfa was stronger than that of wolfberry in the range of 30—90 cm horizontally and 0—60 cm vertically. The competitive ability of alfalfa gradually weakened with increasing distance from the wolfberry row and the soil surface. The interspecific competition intensity of wolfberry-alfalfa intercropping decreased with increasing distance from the wolfberry row. Competition intensity could be divided into three areas: high-intensity competition area, medium-intensity competition area, and low-intensity competition area (0—60, 60—90 cm, and 90—150 cm, respectively). It is recommended that intercropped alfalfa should be planted 60 cm away from the wolfberry row. [Conclusion] Intensive intercropping of forest and grass results in crop biomass migrating and decreasing due to weak competition for aboveground space, thereby inhibiting plant growth. In order to effectively reduce the competition for aboveground space between forests and grasses in forest-grass intercropping, the competition and stress of forages on forest trees should be reduced by appropriately increasing the planting distance between trees and forages, thereby enabling trees to obtain better growth space. Pastures should be grown outside areas of higher competition.