The invention discloses a plant-derived pesticide for controlling underground pests. The plant-derived pesticide for controlling underground pests is prepared according to the following steps: uniformly mixing 1.5 to 2.5% by volume of trehalose, 0.2 to 0.8% by volume of chitosan and the balance of traditional Chinese medicine components to prepare a traditional Chinese medicine-containing active mixed medium; and inoculating a composite microbial strain into the traditional Chinese medicine-containing active mixed medium for fermentation culture until the concentration of microorganisms reaches 3.0 billion strains/mL, so as to obtain the plant-derived pesticide for controlling underground pests. The traditional Chinese medicine components include all-grass of foxtail-like sophora, radix sophorae flavescentis, eupatorium adenophora, radix curcumae, male fern rhizome, giant knotweed, phellodendron bark, falsehellebore root and rhizome, fructus cnidii and flos caryophylli. The plant-derived pesticide can solve the problem that underground pests cannot be effectively suppressed and the food safety problem brought by application of chemical pesticides in the prior art, and the plant-derived pesticide not only effectively prevents underground pests, but also is friendly to environment and pollution-free and does not bring food safety problems.