The invention relates to the technical field of soilless culture and in particular relates to a soilless culture nutrient solution and a preparation method thereof. According to the soilless culture nutrient solution, the following components are added into every 1L of water by weight: 6-10g of calcium nitrate, 3-5g of potassium nitrate, 3-5g of magnesium sulfate, 2-4g of ammonium phosphate, 0.8-2g of potassium sulfate, 0.8-2g of monopotassium phosphate, 0.08-0.15g of EDTA (Ethylene Diamine Tetraacetic Acid) chelating iron, 0.05-0.08g of ferrous sulfate, 0.02-0.04g of boric acid, 0.1-0.3g of manganese sulfate, 0.003-0.006g of zinc sulfate, 0.001-0.0015g of copper sulfate, 0.001-0.003g of ammonium molybdate, 1-2g of EM probiotic liquid, 6-8g of oligosaccharide and 8-10g of anticorrosive antiseptic substance. Due to adoption of the technical scheme of the invention, the soilless culture nutrient solution has the beneficial effects that the soilless culture nutrient solution is enriched in nutrient substances and wide in application range, and the optimal requirements of flowers on temperature, moisture, illumination, nutrient and air in the growth and development process can be effectively controlled. Moreover, according to the soilless culture nutrient solution, the disease and insect resistance of crops is improved, the yield is high, and the product quality is high.