The invention relates to a method for planting cotton in a saline-alkali land, in particular to a water-saving early sowing method for full cotton seedlings in a saline-alkali land. The method comprises rotary tillage for land preparation and raking for holding water, and comprises the following steps of: digging shallow furrows with the depth of 8 to 10 centimeters for sowing when the total salt content of the soil is less than 0.4 percent, covering the soil of 2 to 3 centimeters after sowing at the bottoms of the furrows, and covering a film on the furrows, wherein the sowing furrows below the film form a greenhouse with the height of 5 to 8 centimeters; digging deep furrows with the depth of 20 to 30 centimeters for sowing when the total salt content of the soil is more than 0.4 percent, watering the furrows, sowing at the positions 10 to 15 centimeters below the land plane beside the furrows when the water content of the soil beside the furrows reaches 80 percent of the maximum water holding quantity, covering the soil of 2 to 3 centimeters, and covering a film on the furrows, wherein the sowing furrows below the film form a greenhouse with the height of 8 to 10 centimeters; pricking a small hole above each reserved seedling when the temperature in the film is more than 40 DEG C in 5 to 7 days after germinating, so that the cotton seedlings are in contact with the external temperature; and releasing the seedlings when the cotton seedlings jack the film in a weak, and heaping soil to plug the holes. By the method, the problems of low cotton seedling emergence rate and difficulty in holding the seedlings in the saline-alkali land are solved.