The invention discloses a water-retention and fertilizer-conservation organic fertilizer supplying method for promoting early growth, quick tillering and robust growth of tobacco seedlings. In the day when tobacco seedlings are transplanted or one day before tobacco seedlings are transplanted, a biological liquid fertilizer, a fish protein organic liquid fertilizer and water are mixed in the volume ratio of 6:(0.2-1):(250-350), and a nutrient solution is obtained for use; dry coco coir and the nutrient solution are mixed at the mass ratio of 1:(5-7), and soaking is conducted for 2-12 hours, and coco coir substrate is obtained for use; before transplanting, the coco coir substrate is embedded in a tobacco pond, and in each pond, the application amount of the dry coco coir is 20-40 g; the tobacco seedlings are planted in the coco coir substrate in the tobacco pond, after transplanting, no water is needed to be sprayed, and a layer of fine dry soil is used for covering the surface layer; topdressing applying, watering, film mulching, seedling pulling-up and pest and disease damage control are conducted according to a conventional young seedling transplanting process. The fertilizer supplying method makes full use of the characteristics, such as loose texture, large porosity, low water content, low volume-weight and high moisture absorbability and moisture retentivity, of the coco coir substrate, the nutrient solution is adopted for supplying fertilizers, and therefore the coco coir substrate can provide sufficient water and fertilizers, can ensure sufficient air gaps and promote early growth, quick tillering and robust growth of the tobacco seedlings.