The invention provides an organic tobacco seedling culturing method. A floating seedling culturing method is adopted for the seedling culturing method. The method includes the following steps that sowing is conducted, high-phosphorus organic seedling culturing substrate is adopted for organic tobacco seedling culturing, a mode that two tobacco seeds are sowed per hole in the edge of a seedling culturing disc, and one tobacco seed is sowed per hole for other holes is adopted in the seedling culturing process, and manual sowing or mechanical sowing is conducted; first fertilizing is conducted in the first main leaf period, second fertilizing is conducted in the third main leaf period; third fertilizing is conducted about 15 days after the second fertilizing is conducted. By means of the method, a mode that inorganic seedling fertilizer is usually adopted for an existing organic tobacco seedling culturing process, and all organification of the seedling culturing process is achieved; besides, the cultured tobacco seedlings are superior to tobacco seedlings cultured through the combination of conventional seedling culturing substrate and inorganic tobacco seedling fertilizer on the aspect of the strong seedling index, root vigor, blade chlorophyll content, seedling recovering time after planting, yield and like; the tobacco seedlings are flourishing in effective roots, spiral roots and water roots are reduced obviously, and algae in a seedling culturing pool is reduced obviously.