The invention discloses an orchard composite green manure and a preparation method thereof. The composite green manure is prepared from the following raw materials by weight: 15-20 parts of orchard waste, 15-25 parts of semen cassiae stems and leaves, 5-10 parts of myriophyllum verticillatum, 10-20 parts of kitchen garbage balls, 3-6 parts of rhamnolipid, 5-10 parts of waste fungus bag, 2-8 partsof polymerized amino acid, 5-10 parts of stevia rebaudian leaf and 3-6 parts of a mixed inoculant. The obtained green manure can provide fruit trees the nutrition required by growth and improve the resistance of the fruit trees themselves, thus realizing control of fruit tree diseases and insect pests, and realizing improvement of soil properties.