In order to clarify the marginal effect of intercropping patterns and the localized maize and soybean intercropping technical patterns in Hetao Irrigation Area of Inner Mongolia, four intercropping technical patterns (row ratio: 2∶3, 2∶4, 4∶3， 4∶4(T2∶3, T2∶4, T4∶3, T4∶4)) were set under the condition of trickle irrigation. The changes of photosynthetic characteristics, interspecific competitiveness and marginal effect were analyzed with maize and soybean as control. The results showed that the overall chlorophyll SPAD and nitrogen content of maize leaves in monocropping and intercropping reached peak at the large trumpet stage, and then decreased gradually, and then appeared a small peak at the filling stage. At this time, the chlorophyll SPAD and nitrogen contents in the T2〖DK〗∶3 mode were not significantly different from those in mono-cropping stage, and the chlorophyll SPAD and nitrogen contents in the large trumpet stage were decreased by 0.91% and 5.07% compared with that in mono-cropping stage, respectively. Compared with monocropping, the net photosynthetic rate was increased by 5.09% and 5.17%, respectively, and reached the peak at the spinneret stage, but T2∶3 decreased slowly compared with monocropping. Other modes were characterized by low peak, early appearance (large trumpet stage), and rapid decline. The contents of chlorophyll SPAD and nitrogen in the leaves of T2∶3 mode and monocropping soybean reached a peak at the flowering stage, and then decreased gradually, and a small peak appeared at the drum grain stage. At pod stage and drum grain stage, the SPAD value and nitrogen content of T2∶3 mode were increased by 2.32% and 5.11%, respectively, compared with that of monocropping. The peak value of net photosynthetic rate appeared late (bulging stage), while the peak value of other models appeared early and decreased rapidly, especially in the middle line of models T2∶4, T4∶3 and T4∶4. Therefore, the long post-anthesis photosynthetic stability period of intercropping populationwas the key, which was an important reason to exert the advantage of intercropping. Only T2∶3 model land equivalent ratio was greater than 1, reaching 1.38, and the relative crowding coefficient of soybean was greater than that of maize, and the encroachment power and competition ratio of intercropping soybean were greater than that of maize. T2∶3 had obvious intercropping advantage and competitiveness, and the relative yield growth of soybean was greater than that of maize, so it was a competitive dominant species. The maize and soybean yields of T2∶3 mode were the highest, which were 9705kg/hm2 and 2265kg/hm2,respectively, accounting for 81.08% and 18.92% of the system yield. Maize yield, chlorophyll SPAD and net photosynthetic rate in T4∶4 mode had significant marginal advantage, while soybean only showed marginal advantage in photosynthetic rate, and middle-line soybean in T2∶3 mode had photosynthetic advantage. In conclusion, T2∶3 model was the appropriate intercropping technology model in Hetao Irrigation Area of Inner Mongolia.