The invention discloses a method for performing multiple cropping of oil sunflower and corn by improving saline and alkaline land. The method comprises the following steps: applying improving fertilizer to planting land, ploughing firstly, then performing rotary tillage, covering a mulching film, and planting oil sunflower; applying the fertilizer and then planting the corn after harvesting the oil sunflower, wherein the improving fertilizer comprises fertilizer A and fertilizer B; the fertilizer A is prepared from flue gas desulfurization gypsum, coal ash, bentonite, zeolite, urea, ammonium phosphate and calcium chloride in a weight ratio of (30 to 40) to (8 to 12) to (20 to 30) to (8 to 12) to (6 to 10) to (6 to 10) to (3 to 5); the fertilizer B is prepared from seaweed meal, cow dung, soybean meal, crop straw and microorganism composite powder in the weight ratio of (45 to 55) to (20 to 30) to (10 to 20) to (6 to 10) to (1 to 3); the microorganism composite powder is prepared from azotobacter chroococcum, trichoderma koningii, clostridium butyricum, bacillus subtilis and German-style lactic acid bacteria in the weight ratio of 1 to 2 to 1 to 1 to 1. By adopting the method, the saline and alkaline land is improved in a green and environment-friendly and pollution-free way, and an outstanding improving effect is achieved; the planted oil sunflower can be taken as a commercialcrop as well as an ornamental landscape plant, multiple cropping of the corn can be realized, the economic benefit is increased, and the environment is beautified.