The invention discloses a method for increasing output of summer corn by improving saline-alkali land based on plant symbiotic relationship, which belongs to the technical field of agriculture cultivation. The method comprises: firstly planting wheat on the saline-alkali land; after the period of seedling establishment of the wheat in the second year, sowing common seepweed herb of saline land in the wheat field, fertilizing and irrigating the wheat land; and establishing symbiotic relationship between the wheat and the common seepweed herb. The growth amount of the common seepweed herb is greatly increased; salt in the saline-alkali land is effectively moved out through salt absorption effect of large amount of the common seepweed herb; the salt content in the land is reduced and the water content in the land is stabilized, thus providing a good environment for the growth of corn; during the harvesting period of the wheat, the wheat and the common seepweed herb are harvested and moved out; after that, corn is planted and the corn is fertilized with few mount and multiple times; nitrogen phosphorus fertilizer is more applied to the corn, thus ensuring the requirement of the corn for nitrogen fertilizer; and through planting management, significantly increased output of the corn is finally realized. According to the invention, by improving the saline-alkali land to increase the output of the summer corn, the value of agricultural production is increased; and the harvesting amount of the common seepweed herb is increased, thus the source of increasing income of a farmer is broadened.