The invention discloses a nutrition solution for horticultural plant floriculture and a preparation method thereof. The nutrition solution for horticultural plant floriculture is prepared from, by weight, 25-35 parts of bud extract, 20-25 parts of gamma-polyglutamic acid, 11-18 parts of wormcast, 6-11 parts of gamma-polyglutamic acid, 10-15 parts of fruit kernel and fruit skin, 8-15 parts of fruit kernel and fruit skin, and 11-12 parts of wheat germ, 6-12 parts of citric acid and 8-11 parts of magnesium sulfate heptahydrate. The adopted bud extract, gamma-polyglutamic acid, wormcast, fruit kernel and fruit skin, gamma-polyglutamic acid, fruit kernel and fruit skin and wheat germ are used as main raw materials. A rooting agent, ground phosphate rock, cobalt chloride and an EM probiotics liquid are added to the raw materials, so that the prepared soilless culture nutrition solution is capable of facilitating balanced absorption of nutrient elements in all growth periods of horticulture culture plants, and the nutrition solution has the functions of plant nutrient increasing, plant growth promotion, plant resistance improvement and plant disease resisting. The components of the rooting agent and the ground phosphate rock can be used for adjusting and stimulating plant growth and improving disease resistance of the plants.