The invention discloses a water-retention soilless culture medium, belonging to the field of agriculture cultivation technique. The water-retention soilless culture medium comprises the following components in percentage by weight: 20-30 percent of organic fertilizer, 10-15 percent of grass carbon, 16-20 percent of fine sand, 8-12 percent of rough sand, 8-12 percent of vermiculite, 5-8 percent of perlite, 5-7 percent of calcium potassium magnesium powder, 3-6 percent of weathered coal, 3-5 percent of ground phosphate rock, 1-2 percent of bentonite, and 0.4-0.8 percent of water-retention agent, wherein the organic fertilizer is prepared by mixing, fermenting and bubbling animal excrements, plant straws and the like, and has moisture rate of 8-15 percent after being aired and screened, the granularity of grass carbon, vermiculite and perlite is smaller than 60 meshes, and the granularity of other components is less than 80 meshes. The preparation method comprises the steps of weighing all components according to proportion, agitating and mixing, drying, inspecting, metering and packaging. The water-retention soilless culture medium has the advantages of being simple in production technique, reasonable in proportion and excellent in applicability, and can be widely applied for breeding and transplantation of tree seedlings and grasses, as well as vegetable, fruits, grains, flowers, trees and the like in drought, deserts and salinization regions.