The invention relates to a pueraria peduncularis extract and osthole insecticidal composition for preventing agricultural pests, the weight ratio of active components of pueraria peduncularis extract to osthole in the insecticidal composition is 1:3 to 3:1, and further the insecticidal composition is prepared into microemulsion. Compared with a single agent, the insecticidal composition has the advantages of broad insecticidal spectrum and synergistic effect, can effectively reduce use cost, reduces pest resistance to insecticides, and can effectively prevent the diamondback moth, cabbage caterpillar, corn armyworm, tea geometrid, empoasca flavescens and other agricultural pests.