The invention relates to the technical field of bactericide compounding, and discloses a bactericide for afforestation tree disease damage prevention and control and a preparation method thereof. Effective ingredients of the bactericide are mainly prepared from Chinese pulsatilla roots, black nightshade herb, artemisia annua, herba violae, radix stemonae, garlic, radix clematidis, fructus chebulae, cortex phellodendri, an adhesive, a thickening agent, a lubricating agent and water. The preparation method of the bactericide mainly comprises the steps of washing, filtering, preparing and the like. The bactericide has a good disease damage prevention and control effect on common urban afforestation disease damages such as anthracnose, powdery mildew and a rust disease; in addition, all the adopted main ingredients are Chinese herb plants beneficial for a human body and the environment and are good in proportioning effect, friendly to urban ecology, free of toxic and side effects on people and livestock and high in using safety; the preparation method of the bactericide is easy and convenient to operate and can be circularly put into use, and therefore the method is suitable for being applied and popularized in urban afforestation projects.