The invention relates to the technical field of soilless culture nutrient solutions, and particularly relates to a plant hydroponic nutrient solution and a preparation method thereof. The plant hydroponic nutrient solution is prepared from the following raw materials in parts by weight: 20 to 30 parts of corn stalks, 15 to 20 parts of tea tree saw dust, 14 to 22 parts of fruit peel, 20 to 30 parts of seaweed, 5 to 10 parts of chicken manure, 1 to 3 parts of plant lactobacillus, 1 to 2 parts of enterococcus faecalis, 1 to 3 parts of protease, 25 to 30 parts of swamp soil, 50 to 80 parts of pond mud, 8 to 10 parts of vinegar and 6 to 10 parts of compound nutrient solution. The plant hydroponic nutrient solution of the invention has the advantages of reasonable formula and balanced nutrition, does not cause harm to cultivation environment and plants, has strong practicability and is suitable for popularization in the field.