The invention relates to the technical field of biogas slurry, and discloses a plant hydroponic nutrient solution prepared from biogas slurry and a preparation method, the plant hydroponic nutrient solution comprises the following raw materials by weight: 1-2 parts of main elements, 1-2 parts of secondary elements, 100-150 parts of water, 2-2.5 parts of adjusting elements, and 1-1.5 parts of eliminating elements. According to the invention, main elements and secondary elements are diluted in water, and meanwhile, calcium nitrate, potassium nitrate, magnesium sulfate, monopotassium phosphate, manganese sulfate, magnesium chloride, potassium permanganate, zinc sulfate, copper sulfate and boric acid in the main elements and the secondary elements are absorbed by water, so that the main elements and the secondary elements can supplement elements contained in the water; the water contains richer nutrition, the nutrition of the plants is supplemented, the root systems of the plants are more developed, the plants grow better, and the effect of improving the survival rate of the plants is achieved.