The invention belongs to the technical field of agricultural culture, and relates to a water-retaining soilless culture substrate and a production method thereof. The method includes using cow manure and pig manure as organic matters, smashing the cow manure and the pig manure to the diameter below 5 millimeters, mixing according to the weight ratio of 1:1, adding clear water to enable water content of the mixture to reach 45%, adding 0.2% of organic fertilizer for fermenting special micro-ecological active microbial agents, controlling the environmental temperature within a range from 15 DEG C to 35 DEG C for piling fermentation after sufficient and even stirring, raking completely from top to bottom once every five days, and drying for standby after 20 days; and proportioning, by weight, 30-50% of biological organic fertilizer, 5-10% of peat, 10-15% of fine sand, 5-8% of coarse sand, 8-20% of weathered coal, 1-3% of ground phosphate rock, 2-8% of vermiculite, 1-5% of perlite, 2-5% of calcium magnesium potassium mineral powder, 1-7% of medical stone and 0.1-0.5% of water-retaining agent, mixing the eleven components according to the proportions, smashing the mixture to below 0.5cm, metering and packaging so that the water-retaining soilless culture substrate is produced.